View source for Avgas

{{short description|Aviation fuel}}
{{Use mdy dates|date=January 2022}}
{{Use American English|date=January 2022}}
{{Globalize|article|USA|2name=the United States|date=July 2015}}
[[File:AmericanAviationAA-1YankeeC-FBVQrefueling01.jpg|thumb|upright=1.14|An [[Grumman American AA-1|American Aviation AA-1 Yankee]] being refueled with 100LL avgas]]

'''Avgas''' ('''aviation gasoline''', also known as '''aviation spirit''' in [[British English]]) is an [[aviation fuel]] used in aircraft with spark-ignited [[internal combustion engine]]s. ''Avgas'' is distinguished from conventional [[gasoline]] (petrol) used in [[motor vehicle]]s, which is termed ''mogas'' (motor gasoline) in an aviation context. Unlike motor gasoline, which has been formulated without lead since the 1970s to allow the use of [[catalytic converter]]s for pollution reduction, the most commonly used grades of avgas still contain [[tetraethyllead|tetraethyl lead]], a toxic lead-containing additive used to aid in [[lubrication]] of the engine, increase [[octane rating]], and prevent [[engine knocking]] (spark-knock). There are ongoing efforts to reduce or eliminate the use of lead in aviation gasoline.

[[Kerosene]]-based [[jet fuel]] is formulated to suit the requirements of [[gas turbine|turbine]] engines which have no octane requirement and operate over a much wider [[flight envelope]] than piston engines. Kerosene is also used by most diesel piston engines developed for aviation use, such as those by [[SMA Engines]], [[Austro Engine]], and [[Thielert Centurion|Thielert]].

==Properties==
The main [[petroleum]] component used in blending avgas is [[alkylate]], which is a mixture of various [[2,2,4-Trimethylpentane|isooctanes.]] Some refineries also use [[reformate]]. All grades of avgas that meet CAN 2–3{{Explain|date=December 2021}}, 25-M82{{Explain|date=December 2021}} have a [[density]] of {{convert|6.01|lb/USgal|g/L}} at {{cvt|15|C}}. (6&nbsp;lb/U.S. gal is commonly used in America for [[weight and balance]] computation.)<ref name=FAAPHAK>{{cite book|title=Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25A)|publisher=[[FAA]]|pages=section 9–7}}</ref> Density increases to {{convert|6.41|lb/USgal|g/L}} at {{cvt|−40|C}}, and decreases by about 0.1% per {{convert|1|C-change}} increase in temperature.<ref name="From The Ground Up">{{cite book
 |last1= MacDonald
 |first1= Sandy A. F.
 |first2 = Isabel L.
 |last2 = Peppler
 |title= From The Ground Up
 |orig-year= 1941
 |edition= Millennium
 |year=2004
 |publisher= Aviation Publishers Co. Limited
 |location= Ottawa, Ontario, Canada
 |isbn= 978-0-9680390-5-2
 |pages= 265, 261
 |chapter= Chapter 10. Airmanship
}}</ref><ref name="CFS">[[Nav Canada]]: ''[[Canada Flight Supplement]]'', page A40. Nav Canada, November 23, 2006</ref>
Avgas has an [[emission factor|emission coefficient]] (or factor) of {{convert|18.355|lb/USgal|kg/L}} of [[carbon dioxide|CO<sub>2</sub>]]<ref name="US DOE EIA  Carbon Dioxide Emissions Coefficients">{{cite web
|author=US Energy Information Administration
|title=Carbon Dioxide Emissions Coefficients
|year=2017
|work=US Energy Information Administration website
|url=http://www.eia.gov/environment/emissions/co2_vol_mass.cfm
|location=Washington, DC
|access-date=February 12, 2017
|archive-date=February 13, 2017
|archive-url=https://web.archive.org/web/20170213164221/http://www.eia.gov/environment/emissions/co2_vol_mass.cfm
|url-status=live
}}</ref><!-- find replacement link for 18.355 figure <ref name="US DOE EIA 2007">{{cite web
 |author=US Energy Information Administration
 |title=Voluntary Reporting of Greenhouse Gases Program – Fuel and Energy Source Codes and Emission Coefficients
 |year=2007
 |work=US Energy Information Administration website
 |location=Washington, DC
 |url=http://www.eia.doe.gov/oiaf/1605/factors.html |archive-url=https://web.archive.org/web/20000407063338/http://www.eia.doe.gov:80/oiaf/1605/factors.html |url-status=dead |archive-date=April 7, 2000 |access-date= December 3, 2007
}}</ref> --><ref name="US DOE EIA 2005">{{Cite book
 |author      = US Energy Information Administration
 |author-link = Energy Information Administration
 |title       = Form EIA-1605EZ Short Form for Voluntary Reporting of Greenhouse Gases
 |chapter     = Appendix F. Fuel and Energy Source Codes and Emission Coefficients
 |chapter-url = ftp://ftp.eia.doe.gov/pub/oiaf/1605/cdrom/pdf/FormEIA-1605EZ_2005.pdf
 |page        = 22
 |year        = 2005
 |place       = Washington, DC
 |url         = ftp://ftp.eia.doe.gov/pub/oiaf/1605/cdrom/pdf/FormEIA-1605EZ_2005.pdf
 |access-date  = December 3, 2007
}}{{Dead link|date=August 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> or about 3.07 units of weight {{CO2}} produced per unit weight of fuel used. Avgas is less volatile, with a Reid [[vapor pressure]] range of 5.5 to 7 psi, than automotive gasoline, with a range of 8 to 14 psi. A minimum limit ensures adequate volatility for engine starting. The upper limits are related to [[atmospheric pressure]] at sea level, 14.7 psi, for motor vehicles and ambient pressure at 22,000&nbsp;ft, 6.25 psi, for aircraft. The lower avgas volatility reduces the chance of [[vapor lock]] in fuel lines at altitudes up to 22,000&nbsp;ft.<ref>Petroleum prehistoric to petrochemicals, G.A.Purdy 1957, Copp Clark Publishing Company, Vancouver, Toronto, Montreal, p.312 and 342</ref>

The particular mixtures in use today are the same as when they were first developed in the 1940s, and were used in airline and military aero engines with high levels of [[supercharger|supercharging]]; notably the [[Rolls-Royce Merlin]] engine used in the Spitfire and Hurricane fighters, Mosquito fighter-bomber and [[Avro Lancaster|Lancaster]] heavy bomber (the Merlin II and later versions required 100-octane fuel), as well as the liquid-cooled [[Allison V-1710]] engine, and air-cooled radial engines from Pratt & Whitney, Wright, and other manufacturers on both sides of the Atlantic. The high [[octane rating]]s were traditionally achieved by the addition of [[tetraethyllead]], a highly toxic substance that was [[Tetraethyllead#Phaseout and ban|phased out of automotive use in most countries]] in the late 20th century.

Leaded avgas is currently available in several grades with differing maximum lead concentrations.  (Unleaded avgas is also available.)  Because tetraethyllead is a toxic additive,  the minimum amount needed to bring the fuel to the required octane rating is used; actual concentrations are often lower than the permissible maximum.{{Citation needed|date=July 2011}} Historically, many post-WWII developed, low-powered 4- and 6-cylinder piston aircraft engines were designed to use leaded fuels; an unleaded replacement fuel is being developed and certified for these engines.  Some reciprocating-engine aircraft still require leaded fuels, but some do not, and some can burn unleaded gasoline if a special oil additive is used.
  
==Consumption==
The annual US usage of avgas was {{convert|186|e6USgal|m3}} in 2008, and was approximately 0.14% of the motor gasoline consumption. From 1983 through 2008, US usage of avgas declined consistently by approximately {{convert|7.5|e6USgal|m3}} each year.<ref>{{cite web|url=http://tonto.eia.doe.gov/dnav/pet/pet_cons_prim_dcu_nus_a.htm|title=U.S. Prime Supplier Sales Volumes of Petroleum Products|author=US Energy Information Administration|access-date=2007-05-27|archive-date=2010-10-03|archive-url=https://web.archive.org/web/20101003223115/http://tonto.eia.doe.gov/dnav/pet/pet_cons_prim_dcu_nus_a.htm|url-status=live}}</ref>  As of 2024, the annual US usage of avgas was {{convert|180|e6USgal|m3}},<ref name="Avgasissue">{{cite web|url=https://www.avweb.com/insider/avgas-issue-comes-to-a-head-and-its-about-time|title=Avgas Issue Comes To A Head And It's About Time|date=February 19, 2024 |access-date=2024-05-26}}</ref> most of which contained lead,<ref name = "whenwill">{{cite web|url=https://www.flyingmag.com/when-will-we-see-unleaded-av-gas/|title=When will we see unleaded AvGas?|date=August 5, 2019 |access-date=2024-05-26}}</ref> and 170,000 aircraft in the US used leaded avgas.<ref name= "whenwill" />

In Europe, avgas remains the most common piston-engine fuel.  High prices have encouraged efforts to convert to [[diesel engines]] burning [[jet fuel]], which is more readily available, less expensive, and has advantages for aviation use.<ref>{{cite web|url=https://www.shell.com/business-customers/aviation/aeroshell/knowledge-centre/technical-talk/techart12-30071515.html|title=AVGAS Facts and Future|website=www.shell.com|access-date=August 27, 2018|archive-date=August 27, 2018|archive-url=https://web.archive.org/web/20180827075347/https://www.shell.com/business-customers/aviation/aeroshell/knowledge-centre/technical-talk/techart12-30071515.html|url-status=live}}</ref>

==Grades==
Grades of avgas are identified by two numbers associated with its
[[octane rating#Motor Octane Number (MON)|Motor Octane Number (MON)]].<ref name="AVGas, Lead, and Engine Relationship">{{cite web
|url= http://www.avweb.com/news/pelican/182149-1.html
|title= Lead in the Hogwash
|access-date= November 18, 2011
|publisher= AV Web
|date= April 2002
|archive-date= January 16, 2012
|archive-url= https://web.archive.org/web/20120116170833/http://www.avweb.com/news/pelican/182149-1.html
|url-status= live
}}</ref> The first number indicates the octane rating of the fuel tested to "[[mixture control|aviation lean]]" standards, which is similar to the [[octane rating#Anti-Knock Index (AKI) or (R+M)/2|anti-knock index]] or "pump rating" given to automotive gasoline in the US. The second number indicates the octane rating of the fuel tested to the "[[mixture control|aviation rich]]" standard, which tries to simulate a supercharged condition with a rich mixture, elevated temperatures, and a high manifold pressure. For example, '''100/130''' avgas has an octane rating of 100 at the lean settings usually used for cruising and 130 at the rich settings used for take-off and other full-power conditions.<ref name="GroundUp20th">{{cite book |page=20 |isbn=0-9690054-2-3|title=From the Ground up|last1=MacDonalds|first1=Sandy A. F.|publisher=Aviation Publishers }}</ref>

[[Antiknock agent]]s such as [[tetraethyl lead]] (TEL) help to control detonation and provide lubrication. One gram of TEL contains 640.6 milligrams of [[lead]].

{{anchor |Table of aviation fuel grades}}
{| class="wikitable sortable" | border="1" cellpadding="2" cellspacing="0"
|+ Table of aviation fuel grades
|-
! scope="col" | Grade
! scope="col" | Colour (Dye)
! scope="col" | Lead (Pb) content maximum (g/L)
! scope="col" class="unsortable" | Additives
! scope="col" class="unsortable" | Uses
! scope="col" class="unsortable"| Availability

|-
| 80/87<br />{{nowrap|("avgas 80")}}
| red + a little blue
| 0.14
| TEL
| It was used in engines with low [[compression ratio]].
| Phased out in late 20th century.
|-
| 82UL
| purple<br />{{nowrap|(red + blue)}}
| 0
| ASTM D6227; similar to automobile gasoline
|
| {{As of|2008}}, 82UL is not being produced.<ref name="ShellAvgasSpecs" /><ref name="AvWeb20071117">{{cite web |last=Pew |first=Glenn |date=November 2007 |title=Avgas: Group Asks EPA To Get The Lead Out |url=http://www.avweb.com/avwebflash/news/GroupAsksEPAToGetTheLeadOutOfAvgas_196596-1.html |url-status=live |archive-url=https://web.archive.org/web/20080224152525/http://www.avweb.com/avwebflash/news/GroupAsksEPAToGetTheLeadOutOfAvgas_196596-1.html |archive-date=February 24, 2008 |access-date=February 18, 2008}}</ref>
|-
| 85UL
| none
| 0
| oxygenate-free
| piston-engine ultralight aircraft. Motor Octane Number min 85. Research Octane Number min 95.<ref>{{cite web|url=http://www.obr.pl/en-GB/avgas_obr_95_aviation_gasoline_a.html|title=85 UL aviation gasoline – OBR|publisher=Obr.pl|access-date=May 22, 2013|archive-url=https://web.archive.org/web/20141128154735/http://www.obr.pl/en-GB/avgas_obr_95_aviation_gasoline_a.html|archive-date=November 28, 2014|url-status=dead}}</ref>
|
|-
| 91/96
| brown<ref name=ASTM_D910/><!-- Sweden mandates that this grade not be dyed (contrary to ASTM D910) because its lead content is almost negligible. See further details in "Phase-out" section of this article.--><br />
| 0.15<ref>{{Cite web |date=1984-07-18 |title=Use of Alternate Grades of Aviation Gasoline for Grade 80/87, and Use of Automotive Gasoline |url=https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC91-33A.pdf |website=www.faa.gov}}</ref>
| TEL
| Made particularly for military use.
| phased out in 1960s <ref>{{cite web | url=https://www.aopa.org/news-and-media/all-news/2022/july/pilot/unleaded-fuels-fueling-safety | title=Fueling safety | date=January 7, 2022 }}</ref>
|-
| 91/96UL
| none
| 0
| ethanol-free, antioxidant and antistatic additives;<ref>{{cite web|url=http://www.obr.pl/en-GB/avgas_91_ul_aviation_gasoline_a.html|title=UL 91 aviation gasoline – OBR|publisher=Obr.pl|access-date=May 21, 2013|archive-url=https://web.archive.org/web/20141129042530/http://www.obr.pl/en-GB/avgas_91_ul_aviation_gasoline_a.html|archive-date=November 29, 2014|url-status=dead}}</ref> ASTM D7547
| In 1991, Hjelmco Oil introduced 91/96UL (also meeting leaded grade 91/98 standard ASTM D910) in Sweden. The fuel can be used in more than 90% of the piston aircraft fleet worldwide.<ref name="RotaxApril2009">{{cite web|title= Selection of Suitable Operating Fluids for 912 and 914 (series) Engines – rev 2|url= http://legacy.rotax-owner.com/si_tb_info/serviceinfo/si-912-016.pdf|access-date= October 31, 2010|last= [[Rotax]]|date= April 2009|archive-date= July 15, 2011|archive-url= https://web.archive.org/web/20110715204129/http://legacy.rotax-owner.com/si_tb_info/serviceinfo/si-912-016.pdf|url-status= live}}</ref><ref name="Teledyne24Jan91">{{cite web|title= Teledyne Continental Letter|url= http://www.hjelmco.com/upl/files/2911.pdf|access-date= February 13, 2010|last= Wheelock|first= Jim|date= January 1991|archive-date= July 11, 2011|archive-url= https://web.archive.org/web/20110711171939/http://www.hjelmco.com/upl/files/2911.pdf|url-status= live}}</ref><ref name="Lyc1070">{{cite web |title=Specified Fuels for Spark Ignited Gasoline Aircraft Engine Models |url=https://www.lycoming.com/service-instruction-no-1070-AB |website=Textron Lycoming |publisher=Lycoming |access-date=2023-02-17 |archive-url=https://web.archive.org/web/20220812221717/https://www.lycoming.com/service-instruction-no-1070-AB |archive-date=2022-08-12 |url-status=live }}</ref><ref name="Kalisz30Oct06">{{cite web|title= Service Bulletin 129/S/2006|url= http://www.hjelmco.com/upl/files/37123.pdf|access-date= February 13, 2010|last= Miring|first= Robert|date= October 2006|archive-date= July 11, 2011|archive-url= https://web.archive.org/web/20110711172014/http://www.hjelmco.com/upl/files/37123.pdf|url-status= live}}</ref><ref>{{cite web|url=http://www.lightaircraftassociation.co.uk/2011/unleaded%20AAN.pdf|title=Rotax Instruction|publisher=lightaircraftassociation.co.uk|year=2011|access-date=May 22, 2013|archive-date=May 13, 2013|archive-url=https://web.archive.org/web/20130513231229/http://www.lightaircraftassociation.co.uk/2011/unleaded%20AAN.pdf|url-status=live}}</ref>
| In 2010, the European Aviation Safety Agency (EASA) cleared this fuel for aircraft engines whose manufacturer has approved it, based on 20 years of trouble-free operations.<ref>{{cite web|title=EASA Safety Information Bulletin 2010–31 : Unleaded Aviation Gasoline (Avgas) Hjelmco 91/96 UL and Hjelmco 91/98 UL|url=http://ad.easa.europa.eu/ad/2010-31|publisher=European Aviation Safety Agency|date=November 8, 2010|access-date=November 6, 2012|archive-date=February 21, 2011|archive-url=https://web.archive.org/web/20110221071137/http://ad.easa.europa.eu/ad/2010-31|url-status=live}}</ref>

|-
| B91/115
| green<br />{{nowrap|(yellow + blue)}}
| 1.60
| TEL; see standard {{nowrap|GOST 1012–72.}}<ref>{{cite web|url=http://www.obr.pl/en-GB/avgas_91115_aviation_gasoline_a.html|title=B 91/115 aviation gasoline – OBR|publisher=Obr.pl|access-date=May 21, 2013|archive-url=https://web.archive.org/web/20141129042532/http://www.obr.pl/en-GB/avgas_91115_aviation_gasoline_a.html|archive-date=November 29, 2014|url-status=dead}}</ref>
| Formulated for [[Shvetsov ASh-62]] and [[Ivchenko AI-14]] – nine-cylinder, air-cooled, radial engines.
| The [[Commonwealth of Independent States]], produced exclusively by Warter (Poland)

|-
| UL94
| purple
| 0
| n/a
| 
| American unleaded fuel developed by Swift Fuels LLC.<ref>{{Cite web |title=Frequently Asked Questions |url=https://www.swiftfuelsavgas.com/faq |access-date=2025-05-28 |website=www.swiftfuelsavgas.com}}</ref>

|-
| 100/130<br />{{nowrap|("avgas 100")}}
| green<br />{{nowrap|(yellow + blue)}}
| 1.12
| TEL
| Mostly replaced by 100LL.
| Southern [[Australia]], [[Chile]]

|-
| 100LL<br />{{nowrap|("avgas 100LL")}}
| blue
| 0.56<ref name=ASTM_D910>{{cite web|title=ASTM D910|url=http://www.astm.org/Standards/D910.htm|publisher=ASTM International|access-date=March 6, 2015|location=West Conshohocken, PA, USA|archive-date=April 2, 2015|archive-url=https://web.archive.org/web/20150402193158/http://www.astm.org/Standards/D910.htm|url-status=live}}</ref>
| TEL; {{cvt|0.56|g/L|g/gal}}<ref name="EAASpecs">{{cite web|url=http://www.eaa.org/autofuel/avgas/avgas_specs.asp |title=Avgas Specifications |access-date=November 30, 2009 |publisher=[[Experimental Aircraft Association]] |year=2009 |url-status=dead |archive-url=https://web.archive.org/web/20100613000045/http://eaa.org/autofuel/avgas/avgas_specs.asp |archive-date=June 13, 2010 }}</ref>{{efn|Similar to the lead content of automotive gasoline from 1973<ref>{{cite web |url=https://www.epa.gov/archive/epa/aboutepa/epa-takes-final-step-phaseout-leaded-gasoline.html |title=EPA Takes Final Step in Phaseout of Leaded Gasoline |quote=Note: this 1996 USEPA document is provided solely to substantiate the 2–3 grams per gallon figure of lead in 1973 on-road automotive gasoline. |access-date=October 19, 2021 |publisher=United States Environmental Protection Agency |year=1996 |archive-date=September 9, 2021 |archive-url=https://web.archive.org/web/20210909213434/https://archive.epa.gov/epa/aboutepa/epa-takes-final-step-phaseout-leaded-gasoline.html |url-status=live }}</ref>}}
| Most commonly used aviation gasoline.
| Common in North America and western Europe

|-
| 100VLL
| blue
| 0.45<ref name=ASTM_D910-11>{{cite web|title=ASTM D910-11|url=http://www.aviation-fuel.com/pdfs/avgas100llspecsastmd910_2011.pdf|publisher=ASTM International|access-date=September 5, 2021|archive-date=April 15, 2016|archive-url=https://web.archive.org/web/20160415123705/http://www.aviation-fuel.com/pdfs/avgas100llspecsastmd910_2011.pdf|url-status=live}}</ref>
| TEL; max {{cvt|0.45|g/L|g/gal}} 
| "Very low lead" substitute for 100LL
|
|-
| G100UL
| green
| 0
| Aromatic compounds such as [[xylene]] or [[mesitylene]]
| Composed primarily of aviation alkylate.
| American unleaded fuel developed by General Aviation Modifications, Inc. Fleet-wide {{Abbr|STC|supplemental type certificate}} approved in 2022.<ref name = gamimakes>{{cite web |title=GAMI makes big announcement at Sun 'n Fun regarding G100UL availability | website=[[YouTube]] | date=April 16, 2024 |url=https://www.youtube.com/watch?v=LkEbd_8HEL8}}</ref><ref name = onemillion>{{cite web |title=More than 1 million gallons of G100 UL unleaded fuel now available |date=May 2024 |url=https://generalaviationnews.com/2024/05/01/more-than-1-million-gallons-of-g100-ul-unleaded-fuel-now-available/}}</ref> Not certified by [[ASTM]].<ref name =Avgasissue />
|-
| 100R
| 
| 0
| n/a
|
| American unleaded fuel developed by Swift Fuels LLC. Received {{Abbr|STC|supplemental type certificate}} in 2024 for Cessna 172 Skyhawk R and S.<ref>{{cite web | url=https://www.aopa.org/news-and-media/all-news/2024/september/26/swift-fuels-100-octane-unleaded-aviation-fuel-granted-first-stc | title=Swift Fuels' 100-octane unleaded aviation fuel granted first STC | date=September 26, 2024 }}</ref>
|-
| UL102
| none
| 0
| n/a
| Blend of 83% [[mesitylene]], 17% [[isopentane]]
| American unleaded fuel developed by Swift Fuels LLC. Limited quantities produced for testing.
|-
| 115/145<br />{{nowrap|("avgas 115")}}
| purple<br />{{nowrap|(red + blue)}}
| 1.29<ref name=MIL-G-5572F>{{cite web|title=MIL-G-5572 Rev F|url=http://everyspec.com/MIL-SPECS/MIL-SPECS-MIL-G/MIL-G-5572F_8746/|date=January 24, 1978|access-date=March 6, 2015|publisher=United States military|archive-date=April 2, 2015|archive-url=https://web.archive.org/web/20150402091651/http://everyspec.com/MIL-SPECS/MIL-SPECS-MIL-G/MIL-G-5572F_8746/|url-status=live}}</ref>
| TEL, historically [[xylidine]]<ref>{{cite web |last1=Meyer |first1=Carl L. |title=Antiknock effectiveness of xylidine in small-scale engines |url=https://ntrs.nasa.gov/citations/19930093446 |website=U.S. NASA NTRS |date=August 1943 |publisher=U.S. Government, NASA |access-date=2 February 2022}}</ref><ref>{{cite web |last1=Starr | first1=Charles E Jr. |display-authors=etal |title=Method of stabilizing xylidine, U.S. Patent No 2,509,891 |url=https://patentimages.storage.googleapis.com/0c/53/cc/4e620bb187e994/US2509891.pdf |website=Google Patents |publisher=U.S. Patent Office |access-date=2 February 2022}}</ref>
| The largest, boost-supercharged radial engines needing this fuel's anti-detonation properties.<ref name="VPRacingFuels">{{cite web|url= http://www.vpracingfuels.com/page469679.html|title= Airplane Racing Fuels|date= September 30, 2010|author=VP Fuels|archive-url=https://web.archive.org/web/20160105001713/http://www.vpracingfuels.com/page469679.html|archive-date=January 5, 2016|url-status= dead}}</ref>
| Limited batches are produced for special events such as air races. Reintroduced by Warter Aviation 2015.<ref>{{Cite web|url=http://pilotweb.aero/news/avgas-115/145-reintroduced-by-warter-aviation-to-give-original-power-back-to-classic-engines-6252974/|title=Avgas 115/145 reintroduced by Warter Aviation to give original power back to classic engines|first=Kate|last=Riordan|date=June 26, 2015}}</ref> 
|}

===100LL (blue)===
[[File:GATS jar 03.JPG|thumb|right|Taking a fuel sample from an under-wing drain using a GATS Jar fuel sampler. The blue dye indicates that this fuel is 100LL.]]

100LL (pronounced "one hundred low lead") may contain a maximum of one-half the tetraethyllead allowed in 100/130 (green) avgas.<ref name=ASTM_D910/><ref name="The Rise and Fall of Tetraethyllead">{{Cite journal|title=The Rise and Fall of Tetraethyllead|journal=Organometallics|volume=22|issue=25|pages=5154–5178|doi=10.1021/om030621b|year=2003|last1=Seyferth|first1=Dietmar|doi-access=}}</ref>

Some of the lower-powered ({{convert|100|-|150|hp|kW|disp=or}}) aviation engines that were developed in the late 1990s are designed to run on unleaded fuel and on 100LL, an example being the [[Rotax 912]].<ref name="RotaxApril2009" />

===Automotive gasoline===
{{More citations needed section|date=July 2025}}
[[File:EAA150.jpg|right|thumb|An EAA Cessna 150 used for American certification of auto fuel]]
Automotive [[gasoline]]—known as mogas or autogas among aviators—that does not contain ethanol may be used in [[type certificate|certified]] aircraft that have a [[Supplemental Type Certificate]] (STC) for automotive gasoline, as well as in [[experimental aircraft]] and [[ultralight aviation|ultralight aircraft]] Some oxygenates other than ethanol are approved, but these STC's prohibit ethanol-laced gasolines. Ethanol-treated gasoline is susceptible to phase-separation which is very possible due to the altitude/temperature changes light airplanes undergo in ordinary flight. This ethanol-treated fuel can flood the fuel system with water which can cause in-flight engine failure. Additionally, the phase-separated fuel can leave remaining portions that do not meet octane requirements due to the loss of the ethanol in the water-absorption process. Further, the ethanol can attack materials in aircraft construction which pre-date "[[gasohol]]" fuels. Most of these applicable aircraft have [[compression ratio|low-compression]] engines which were originally certified to run on 80/87 avgas and require only "regular" 87 [[Research Octane Number|anti-knock index]] automotive gasoline. Examples include the popular [[Cessna 172 Skyhawk]] or [[Piper Cherokee]] with the {{convert|150|hp|abbr=on}} variant of the [[Lycoming O-320]].

Some aircraft engines were originally certified using a 91/96 avgas and have STC's available to run "premium" 91 [[Research Octane Number|anti-knock index]] (AKI) automotive gasoline. Examples include some Cherokees with the {{convert|160|hp|abbr=on}} [[Lycoming O-320]] or {{convert|180|hp|abbr=on}} [[Lycoming O-360|O-360]], or the [[Cessna 152]] with the [[Lycoming O-235|O-235]]. [[Octane rating#Anti-Knock Index (AKI) or (R+M)/2|The AKI rating of typical automotive fuel]] might not directly correspond to the 91/96 avgas used to certify engines, as motor vehicle pumps in the US use the so-called "(R + M)/2" averaged motor vehicle octane rating system as posted on gas station pumps. [[Octane rating#Sensitivity|Sensitivity]] is roughly 8–10 points, meaning that a 91 AKI fuel might have a MON of as low as 86. The extensive testing process required to obtain an STC for the engine/airframe combination helps ensure that, for those eligible aircraft, 91 AKI fuel provides sufficient detonation margin under normal conditions.

Automotive gasoline is not a fully viable replacement for avgas in many aircraft, because many high-performance and/or turbocharged airplane engines have been designed to use 100 octane fuel and modifications are necessary in order to use lower-octane fuel.<ref name="Berry">{{cite web|url=http://www.eaa.org/autofuel/autogas/articles/1Autogas%20vs%20Avgas.pdf|title=Avgas vs Autogas|access-date=December 31, 2008|last=Berry|first=Mike|url-status=dead|archive-url=https://web.archive.org/web/20090220025324/http://www.eaa.org/autofuel/autogas/articles/1Autogas%20vs%20Avgas.pdf|archive-date=February 20, 2009}}</ref><ref name="Berry2">{{cite web|url=http://www.eaa.org/autofuel/autogas/articles/1Autogas%20vs%20Avgas%20Part%202.pdf|title=Autogas Part 2|access-date=December 31, 2008|last=Berry|first=Mike|date=n.d.|url-status=dead|archive-url=https://web.archive.org/web/20100613042650/http://eaa.org/autofuel/autogas/articles/1Autogas%20vs%20Avgas%20Part%202.pdf|archive-date=June 13, 2010}}</ref>

Many [[general aviation]] [[aircraft engine]]s were designed to run on 80/87 octane, roughly the standard (as unleaded fuel only, with the [[Octane rating#Anti-Knock Index (AKI) or (R+M)/2|"{R+M}/2"]] 87 octane rating) for North American automobiles today. Direct conversions to run on automotive fuel are fairly common, by [[supplemental type certificate]] (STC). However, the alloys used in aviation engine construction are chosen for their durability and synergistic relationship with the protective features of lead, and engine wear in the valves is a potential problem on automotive gasoline conversions.

Fortunately, significant history of engines converted to mogas has shown that very few engine problems are caused by automotive gasoline. A larger problem stems from the higher and wider range of allowable vapor pressures found in automotive gasoline; this can pose some risk to aviation users if fuel system design considerations are not taken into account. Automotive gasoline can vaporize in fuel lines, causing a [[vapor lock]] (a bubble in the line) or [[fuel pump]] cavitation, thereby starving the engine of fuel. This does not constitute an insurmountable obstacle, but merely requires examination of the fuel system, ensuring adequate shielding from high temperatures and maintaining sufficient pressure in the fuel lines. This is the main reason why both the specific engine model as well as the aircraft in which it is installed must be supplementally certified for the conversion. A good example of this is the [[Piper Cherokee]] with high-compression {{convert|160|or|180|hp|abbr=on}} engines. Only later versions of the airframe with different engine cowling and exhaust arrangements are applicable for the automotive fuel STC, and even then require fuel-system modifications.

Vapor lock typically occurs in fuel systems where a mechanically-driven fuel pump mounted on the engine draws fuel from a tank mounted lower than the pump. The reduced pressure in the line can cause the more volatile components in automotive gasoline to flash into vapor, forming bubbles in the fuel line and interrupting fuel flow. If an electric boost pump is mounted in the fuel tank to push fuel toward the engine, as is common practice in fuel-injected automobiles, the fuel pressure in the lines is maintained above ambient pressure, preventing bubble formation. Likewise, if the fuel tank is mounted above the engine and fuel flows primarily due to gravity, as in a high-wing airplane, vapor lock cannot occur, using either aviation or automotive fuels. Fuel-injected engines in automobiles also usually have a "fuel return" line to send unused fuel back to the tank, which has the benefit of equalizing the fuel's temperature throughout the system, further reducing the chance of vapor lock developing.

In addition to vapor locking potential, automotive gasoline does not have the same quality tracking as aviation gasoline. To help solve this problem, the specification for an aviation fuel known as 82UL was developed as essentially automotive gasoline with additional quality tracking and restrictions on permissible additives. This fuel is not currently in production and no refiners have committed to producing it.<ref name="AvWeb20071117"/>

===Gasohol===
{{See also|Common ethanol fuel mixtures#E10 or less}}
Rotax allows up to 10% ethanol (similar to [[E10 fuel]] for cars) in the fuel for [[Rotax 912]] engines. Light sport aircraft that are specified by the manufacturer to tolerate alcohol in the fuel system can use up to 10% ethanol.<ref name="RotaxApril2009" />

===Fuel dyes===
[[Fuel dyes]] aid ground crew and pilots in identifying and distinguishing the fuel grades<ref name="ShellAvgasSpecs">{{cite web
|url=http://www.shell.com/home/content/aviation-en/productservice/aviationfuels/detail/avgasgradesspecs_10081006.html
|title=Avgas Grades and Specification|access-date= November 30, 2009
|publisher=Shell Aviation
|date=July 2008
|archive-url=https://web.archive.org/web/20080714154427/http://www.shell.com/home/content/aviation-en/productservice/aviationfuels/detail/avgasgradesspecs_10081006.html
|archive-date=July 14, 2008}}</ref>
and most are specified by ASTM D910 or other standards.<ref name=ASTM_D910/>
Dyes for the fuel are required in some countries.<ref>{{cite web
|publisher=CSG
|title=Aviation Fuel – AvGas Information Aviation Gasoline
|url=http://www.csgnetwork.com/avgas.html
|access-date=May 10, 2012
|archive-date=May 25, 2012
|archive-url=https://web.archive.org/web/20120525061351/http://www.csgnetwork.com/avgas.html
|url-status=live
}}</ref>

{| class="wikitable sortable" | border="1" cellpadding="2" cellspacing="0"
|+ Table of aviation fuel dyes
|-
! scope="col" | Dye (nominal colour)
! scope="col" | chemical

|-
|blue
|alkyl derivatives of 1,4-diaminoanthraquinone, like [[Oil Blue A]] and [[Oil Blue 35]]
|-
|yellow
|[[Solvent Yellow 56|p-diethylaminoazobenzene]] or 1,3-benzenediol, 2,4-bis [(alkylphenyl)azo-]
|-
|red
|alkyl derivatives of [[Sudan III|azobenzene-4-azo-2-naphthol]]
|-
|orange
|[[Sudan I|benzene-azo-2-napthol]]
|}

==Phase-out of leaded aviation gasoline==
The 100LL phase-out has been called "one of modern GA's most pressing problems",<ref name=aeromarkt235>{{cite news
|url=http://www.aeromarkt.net/index.php?lng=1&cll=archive&ID=619
|title=Avgas Revolution?
|work=Aeromarkt
|issue=235
|department=Editorial
|date=August 2008
|access-date=August 28, 2008
|archive-date=July 23, 2011
|archive-url=https://web.archive.org/web/20110723002943/http://www.aeromarkt.net/index.php?lng=1&cll=archive&ID=619
|url-status=dead
}}</ref> because 70% of 100LL aviation fuel is used by the 30% of the aircraft in the general aviation fleet that cannot use any of the existing alternatives.<ref name=AOPAalternatives>
{{cite web
|title=Regulatory Brief: AVGAS (100LL) ALTERNATIVES
|url=http://www.aopa.org/whatsnew/regulatory/regunlead.html
|author=Aircraft Owners and Pilots Association
|date=August 9, 2006
|access-date=August 28, 2008
|archive-url= https://web.archive.org/web/20080802040502/http://www.aopa.org/whatsnew/regulatory/regunlead.html
|archive-date= August 2, 2008 |url-status= live}}</ref><ref name=AirportBusinessAugust2008>{{cite news
|url=http://www.airportbusiness.com/web/online/Top-News-Headlines/Swift-developing-synthetic-fuel-to-replace-100LL/1$20599
|title=Swift developing synthetic fuel to replace 100LL
|author=Taylor Graham
|work=Airport Business News
|publisher=Airport Business
|date=August 28, 2008
|access-date=August 28, 2008
|archive-url=https://web.archive.org/web/20110707100551/http://www.airportbusiness.com/web/online/Top-News-Headlines/Swift-developing-synthetic-fuel-to-replace-100LL/1$20599
|archive-date=July 7, 2011
|url-status=dead
}}</ref><ref name=AOPA10ll>
{{cite web
 |url=http://www.aopa.org/aircraft/articles/2008/080319avgas.html 
 |title=AOPA working on future avgas 
 |author=AOPA ePublishing staff 
 |work=AOPA online 
 |publisher=Aircraft Owners and Pilots Association 
 |date=March 19, 2006 
 |access-date=August 28, 2008 
 |url-status=dead 
 |archive-url=https://web.archive.org/web/20080621063155/http://www.aopa.org/aircraft/articles/2008/080319avgas.html 
 |archive-date=June 21, 2008 
}}</ref>

There are three fundamental issues in using unleaded fuels without serious modification of the airframe/engine:
# The fuel must have a high enough octane rating (and meet other specifications) to replace leaded fuels,
# The engine must be certified to use the fuel, and
# The airframe must also be certified to use the fuel.<ref>{{cite web |last1=Schauk |first1=M. E. |title=Certification of a Carbureted Aircraft Engine on Ethanol Fuel |url=https://afdc.energy.gov/files/pdfs/2896.pdf |publisher=Baylor University |access-date=17 February 2023}}</ref>

In February 2008, [[Teledyne Continental Motors]] (TCM) announced that the company is very concerned about future availability of 100LL, and as a result, they would develop a line of [[diesel engine]]s.<ref name="AvWeb18Feb08">{{cite web
|title= Teledyne Continental Plans Certified Diesel Within Two Years
|url= http://www.avweb.com/eletter/archives/avflash/1054-full.html
|access-date= February 18, 2008
|last= AvWeb Staff| date=February 2008 |archive-url= https://web.archive.org/web/20080226084557/http://www.avweb.com/eletter/archives/avflash/1054-full.html
|archive-date= February 26, 2008 |url-status= live}}</ref>
In a February 2008 interview, TCM president [[Rhett Ross]] indicated belief that the aviation industry will be "forced out" of using 100LL in the near future, leaving automotive fuel and jet fuel as the only alternatives. In May 2010, TCM announced that they had licensed development of the [[SMA SR305-230|SMA SR305]] diesel engine.<ref name="Bertorelli">{{cite web
|title= Make Room in the Aerodiesel Market, Thielert — TCM Tells Aviation Consumer About Some Big Engine Plans
|url= http://www.avweb.com/podcast/podcast/197170-1.html?kw=RelatedStory
|access-date= February 18, 2008|last= Bertorelli |first= Paul | date=February 2008 |archive-url= https://web.archive.org/web/20080228035038/http://www.avweb.com/podcast/podcast/197170-1.html
|archive-date= February 28, 2008 <!--DASHBot-->}}</ref><ref name="AvWeb12May10">{{cite web
|title= Continental Unveils a Diesel Project
|url= http://www.avweb.com/avwebflash/news/Continental_DieselEngineProject_202535-1.html
|access-date= May 12, 2010|last= Paul|first= Bertorelli |date=May 2010
|archive-url= https://web.archive.org/web/20100515145705/http://www.avweb.com/avwebflash/news/Continental_DieselEngineProject_202535-1.html
|archive-date= May 15, 2010 |url-status= live}}</ref><ref name="AvWeb12May10A">{{cite web
|url= http://www.avweb.com/blogs/insider/AVWebInsider_DieselTCM_202542-1.html
|title= TCM Buys a Diesel: Does This Make Sense?
|access-date= May 13, 2010|last= Paul|first= Bertorelli |date=May 12, 2010
|archive-url= https://web.archive.org/web/20100520023102/http://www.avweb.com/blogs/insider/AVWebInsider_DieselTCM_202542-1.html
|archive-date= May 20, 2010 <!--DASHBot-->}}</ref>

In November 2008, [[National Air Transportation Association]] president Jim Coyne indicated that the environmental impact of aviation is expected to be a big issue over the next few years and will result in the phasing out of 100LL because of its lead content.<ref name="Avweb06Nov08">{{cite web
|url= http://www.avweb.com/news/aopa/AOPAExpo2008_USGovernment_AviationOffWashingtonDCRadar_199142-1.html
|title= Aviation Off D.C. Radar
|access-date= November 7, 2008
|last= Niles
|first= Russ
|date= November 2008
|archive-date= February 9, 2009
|archive-url= https://web.archive.org/web/20090209210655/http://www.avweb.com/news/aopa/AOPAExpo2008_USGovernment_AviationOffWashingtonDCRadar_199142-1.html
|url-status= live
}}</ref>

By May 2012, the US Federal Aviation Administration (FAA Unleaded Avgas Transition rulemaking committee) had put together a plan in conjunction with industry to replace leaded avgas with an unleaded alternative within 11 years. Given the progress already made on 100SF and G100UL, the replacement time might be shorter than that 2023 estimate. Each candidate fuel must meet a checklist of 12 fuel specification parameters and 4 distribution and storage parameters. The FAA has requested a maximum of US$60M to fund the administration of the changeover.<ref name="Bertorelli20May12">{{cite news
|url= http://www.avweb.com/avwebflash/news/11_Year_Timeline_For_Fuel_Replacement_206713-1.html
|title= FAA Fuel Committee: 11-Year Timeline for Avgas Replacement
|access-date= May 21, 2012
|last= Bertorelli
|first= Paul
|date= May 20, 2012
|work= AVweb
|archive-date= July 6, 2012
|archive-url= https://web.archive.org/web/20120706053042/http://www.avweb.com/avwebflash/news/11_Year_Timeline_For_Fuel_Replacement_206713-1.html
|url-status= live
}}</ref><ref name="avnews: future of fuel">{{cite news
|title=The future of fuel
|date=September 29, 2013
|first=Janice
|last=Wood
|work=General Aviation News
|url=http://generalaviationnews.com/2013/09/29/the-future-of-fuel/#more-83306
|access-date=December 12, 2013
|archive-date=August 4, 2014
|archive-url=https://web.archive.org/web/20140804093836/http://generalaviationnews.com/2013/09/29/the-future-of-fuel/#more-83306
|url-status=live
}}</ref> In July 2014, nine companies and consortiums submitted proposals to the ''Piston Aviation Fuels Initiative'' (PAFI) to assess fuels without tetraethyl lead. Phase one testing is performed at the [[William J. Hughes Technical Center]] for a FAA approved industry replacement by 2018.<ref>{{cite journal|journal=AOPA Pilot|date=September 2014|title=FAA to Evaluate nine unleaded fuels|author=Dave Hirschman|page=28}}</ref>

In July 2021, the first commercially-produced unleaded avgas, GAMI's [[#G100UL|G100UL]], was approved by the [[Federal Aviation Administration]] through a [[Supplemental Type Certificate]].<ref name="Bertorelli27Jul21">{{cite web|url= https://www.avweb.com/aviation-news/gami-awarded-long-awaited-stc-for-unleaded-100-octane-avgas/|title= GAMI Awarded Long-Awaited STC For Unleaded 100-Octane Avgas|access-date= 15 July 2021|last= Bertorelli|first= Paul|work= AVweb|date= 27 July 2021|archive-url= https://web.archive.org/web/20210728114042/https://www.avweb.com/aviation-news/gami-awarded-long-awaited-stc-for-unleaded-100-octane-avgas/|archive-date= 28 July 2021|url-status= live}}</ref>

[[Lycoming Engines]] provides a list of engines and fuels that are compatible with unleaded fuel. However, all of their engines require that an oil additive be used when unleaded fuel is used: "When using the unleaded fuels identified in Table 1, Lycoming oil additive P/N LW-16702, or an equivalent finished product such as Aeroshell 15W-50, must be used."<ref name="Lyc1070" /> Lycoming also notes that the octane rating of the fuel used must also meet the requirements stated in the fuel specification, otherwise engine damage may occur due to detonation.
  
Prior to {{YEAR|2022}}, [[Teledyne Continental Motors]] (TCM) indicated that leaded avgas is required in their engines, and not unleaded auto fuels: "Current aircraft engines feature valve gear components which are designed for compatibility with the leaded ASTM D910 fuels. In such fuels, the lead acts as a lubricant, coating the contact areas between the valve, guide, and seat. The use of unleaded auto fuels with engines designed for leaded fuels can result in excessive exhaust valve seat wear due to the lack of lead with cylinder performance deteriorating to unacceptable levels in under 10 hours."<ref>{{cite web |title=Use of Automotive Gasoline in TCM Aircraft Engines |url=https://pceonline.com/wp-content/uploads/2017/04/TCMEngineCareX30548Rev3.pdf |website=Teledyne Continental Motors |publisher=Pacific Continental Motors |access-date=October 3, 2017 |archive-url=https://web.archive.org/web/20171004135916/https://pceonline.com/wp-content/uploads/2017/04/TCMEngineCareX30548Rev3.pdf |archive-date=October 4, 2017 |url-status=dead }}</ref>

In {{YEAR|2022}}, TCM changed its policy. They have announced a formal application to the [[Federal Aviation Administration|FAA]] to approve the use of UL91 and UL94 in selected engines, stating that "Continental considers 91UL and 94UL fuel as a transitional step in a long-term strategy to reach a more sustainable aviation".<ref>{{cite press release |author=<!--Not stated--> |title=Continental Aerospace Technologies Submits Application to FAA for Use of UL 91/94 in Select Engines |url=https://www.continental.aero/xPublications/News%20Releases/Continental%20Aerospace%20Technologies%E2%84%A2%20Announces%2091%20and%2094%20Use%20for%20Select%20Engines/ |format=PDF |location=Oshkosh, Wisconsin, USA |publisher=Continental Aerospace Technologies |date=2022-07-26 |access-date=2023-02-15 |archive-url=https://web.archive.org/web/20221130144356/https://www.continental.aero/xPublications/News%20Releases/Continental%20Aerospace%20Technologies%E2%84%A2%20Announces%2091%20and%2094%20Use%20for%20Select%20Engines/ |archive-date=2022-11-30 |url-status=live}}</ref>

==New unleaded fuel grades==

===91UL (or UL91)===
[[Hjelmco Oil]] first introduced unleaded Avgas grades in Europe in 2003, after its success with 80UL.<ref>{{cite web |title=Hjelmco i dina tankar|url=https://www.hjelmco.com/upl/files/2374.pdf |language=sv |access-date=17 February 2023}}</ref> This grade of Avgas is manufactured to meet ASTM D7547.<ref name=":0" /> Many common Lycoming engines are certified to run on this particular grade of Avgas,<ref name="Lyc1070" /> and [[Cessna]] has approved the use of this fuel in a large number of their piston fleet.<ref>{{cite web |title=FUEL - PLACARD INSTALLATION FOR USE OF VERY LOW LEAD AND UNLEADED AVIATION FUEL|url=https://support.cessna.com/custsupt/contacts/pubs/ourpdf.pdf?as_id=54042 |archive-url=https://web.archive.org/web/20220204070706/https://support.cessna.com/custsupt/contacts/pubs/ourpdf.pdf?as_id=54042 |archive-date=2022-02-04 |url-status=dead}}</ref> This fuel is also usable in any aircraft in Europe<ref>{{cite web |title=May I use Unleaded Aviation Gasoline (Avgas) UL 91 even if the airframe TCDS states that the minimum fuel octane is 100? |url=https://www.easa.europa.eu/en/faq/19380 |website=EASA |access-date=17 February 2023 |language=en}}</ref> or the United Kingdom<ref>{{cite web |title=Introduction of Generic Concession No. 7 (Unleaded Aviation Gasoline (Avgas) UL91 |url=https://publicapps.caa.co.uk/docs/33/20121031Introduction%20of%20Generic%20Concession%20No.7%20(Unleaded%20Aviation%20Gasoline%20(Avgas)%20UL91_3.pdf |access-date=17 February 2023}}</ref> where the engine is certified to use it, whether or not the airframe is certified to do so, too.

===93UL (Ethanol-free 93AKI automotive gasoline)===
The firm Airworthy AutoGas tested an ethanol-free 93 [[Anti-knock index|anti-knock index (AKI)]] premium auto gas on a Lycoming O-360-A4M in 2013. The fuel is certified under Lycoming Service Instruction 1070 and ASTM D4814.<ref>{{cite journal|journal=General Aviation News|date=July 19, 2013|page=5|title=Piper Flies on Auto Gas}}</ref>

===UL94 (formerly 94UL)===
Unleaded 94 [[Motor octane number|Motor octane]] fuel (''UL94'') is essentially 100LL without the lead.
In March 2009, [[Teledyne Continental Motors]] (TCM) announced they had tested a 94UL fuel that might be the best replacement for 100LL. This 94UL meets the avgas specification including vapor pressure but has not been completely tested for detonation qualities in all Continental engines or under all conditions. Flight testing has been conducted in an [[Continental O-550|IO-550-B]] powering a [[Beechcraft Bonanza]] and ground testing in [[Continental O-200]], [[Continental O-240|240]], [[Continental O-470|O-470]], and [[Continental O-520|O-520]] engines. In May 2010, TCM indicated that despite industry skepticism, they are proceeding with 94UL and that certification was expected in mid-2013.<ref name="AvWeb31Mar09">{{cite web
|url= http://www.avweb.com/avwebbiz/news/Continental_94_UL_Replacement_100LL_200048-1.html
|title= Continental: Maybe 94 Unleaded Fuel Will Fly
|access-date= April 13, 2009|last= Bertorelli|first= Paul |date=March 2009
|archive-url= https://web.archive.org/web/20090406013119/http://www.avweb.com/avwebbiz/news/Continental_94_UL_Replacement_100LL_200048-1.html
|archive-date= April 6, 2009 |url-status= live}}</ref><ref name="AvWeb12May10B">{{cite web
|url= http://www.avweb.com/avwebflash/news/TCM_94UL_Replacing_100LL_AlternativeFuels_202536-1.html
|title= Can 94UL Replace 100LL? TCM Thinks So |access-date= May 12, 2010|last= Bertorelli|first= Paul |date=May 2010
|archive-url= https://web.archive.org/web/20100515125025/http://www.avweb.com/avwebflash/news/TCM_94UL_Replacing_100LL_AlternativeFuels_202536-1.html
|archive-date= May 15, 2010 |url-status= live}}</ref>

In June 2010, [[Lycoming Engines]] indicated their opposition to 94UL. Company general manager Michael Kraft stated that aircraft owners do not realize how much performance would be lost with 94UL and characterized the decision to pursue 94UL as a mistake that could cost the aviation industry billions in lost business. Lycoming believes the industry should be pursuing 100UL instead. The Lycoming position is supported by [[aircraft type club]]s representing owners of aircraft that would be unable to run on lower octane fuel. In June 2010, clubs such as the American Bonanza Society, the Malibu Mirage Owners and Pilots Association, and the Cirrus Owners and Pilots Association collectively formed the ''Clean 100 Octane Coalition'' to represent them on this issue and push for unleaded 100 octane avgas.<ref name="AvWeb06Jun10">{{cite web|url= http://www.avweb.com/avwebflash/news/LycomingSays94UL_Would_Be_Mistake_202673-1.html|title= Lycoming: 94UL Would Be A Huge Mistake|access-date= June 14, 2010|last= Bertorelli|first= Paul|date= June 11, 2010|archive-date= June 8, 2010|archive-url= https://web.archive.org/web/20100608204728/http://www.avweb.com/avwebflash/news/LycomingSays94UL_Would_Be_Mistake_202673-1.html|url-status= live}}</ref><ref name="AvWeb11Jun10">{{cite web
|url= http://www.avweb.com/avwebflash/news/lead_fuel_epa_coalition_rulemaking_regulations_aircraft_engine_202711-1.html
|title= Groups Act On Potential Leaded-Fuel Rulemaking
|access-date= June 14, 2010
|last= Pew
|first= Glenn
|date= June 2010
|archive-date= June 11, 2011
|archive-url= https://web.archive.org/web/20110611225346/http://www.avweb.com/avwebflash/news/lead_fuel_epa_coalition_rulemaking_regulations_aircraft_engine_202711-1.html
|url-status= live
}}</ref><ref name="AvWeb16Jun10">{{cite web
|url= http://www.avweb.com/avwebflash/news/BigEngineTypeGroupsUniteOnFuelIssue_202734-1.html
|title= Big-Engine Type Groups Unite On Fuel Issue
|access-date= June 14, 2010
|last= Niles
|first= Russ
|date= June 2010
|archive-date= June 11, 2011
|archive-url= https://web.archive.org/web/20110611225351/http://www.avweb.com/avwebflash/news/BigEngineTypeGroupsUniteOnFuelIssue_202734-1.html
|url-status= live
}}</ref><ref name="100OC">{{cite web
|url= http://www.100octaneformyplane.com/
|title= 100 Octane Unleaded Aviation Fuel – Demand No Less!
|access-date= September 11, 2010|last= Lee|first= B. |year=2010
|archive-url= https://web.archive.org/web/20100830222404/http://www.100octaneformyplane.com/
|archive-date= August 30, 2010 |url-status= live}}</ref>

In November 2015, UL94 was added as a secondary grade of unleaded aviation gasoline to ASTM D7547, which is the specification that governs UL91 unleaded avgas. UL91 is currently being sold in Europe. UL94 meets all of the same specification property limits as 100LL with the exception of a lower [[motor octane number]] (94.0 minimum for UL94 vs. 99.6 minimum for 100LL) and a decreased maximum lead content. UL94 is an unleaded fuel, but as with all [[ASTM International]] unleaded gasoline specifications, a ''[[de minimis]]'' amount of unintentionally added lead is permitted.<ref name=":0">{{Cite web|title=ASTM D7547 – 15e1 Standard Specification for Hydrocarbon Unleaded Aviation Gasoline|website=www.astm.org|url-status=live |url=https://www.astm.org/Standards/D7547.htm|access-date=April 14, 2017|archive-date=April 15, 2017 |archive-url=https://web.archive.org/web/20170415200948/https://www.astm.org/Standards/D7547.htm}}</ref>

Since May 2016, UL94, now a product of Swift Fuels, is available for sale at dozens of airports in the United States. Swift Fuels has an agreement for distribution in Europe.<ref name="AOPA September 13, 2016 94UL">{{cite news
|url=https://www.aopa.org/news-and-media/all-news/2016/september/13/swift-fuels-94ul-put-to-the-test
|title=Swift Fuels 94UL Put to the Test
|access-date=February 12, 2017
|work=AOPA News
|date=September 13, 2016
|author=Dave Hirschman
|archive-date=February 14, 2017
|archive-url=https://web.archive.org/web/20170214002213/https://www.aopa.org/news-and-media/all-news/2016/september/13/swift-fuels-94ul-put-to-the-test
|url-status=live
}}</ref><ref name="Swift Fuel product 94UL">{{cite web
|url=https://swiftfuels.com/fuel/unleaded-ul94-avgas/
|title=Unleaded UL94 Avgas
|access-date=February 12, 2017
|archive-url=https://web.archive.org/web/20170213165149/https://swiftfuels.com/fuel/unleaded-ul94-avgas/
|archive-date=February 13, 2017
|url-status=dead
}}</ref><ref name="AINOnline 6 April2016 94UL 102 UL">{{cite news
|title=Swift Fuels Introduces Unleaded 94UL Avgas Nationwide
|url=http://www.ainonline.com/aviation-news/general-aviation/2016-04-06/swift-fuels-introduces-unleaded-94ul-avgas-nationwide
|work=AINOnline
|publisher=Aviation International News
|date=April 6, 2016
|access-date=February 13, 2017
|last=Laboda
|first=Amy
|archive-date=February 14, 2017
|archive-url=https://web.archive.org/web/20170214003131/http://www.ainonline.com/aviation-news/general-aviation/2016-04-06/swift-fuels-introduces-unleaded-94ul-avgas-nationwide
|url-status=live
}}</ref>

UL94 is not intended to be a full replacement for 100LL, but rather is designed to be a drop-in replacement for aircraft with lower-octane-rated engines, such as those that are approved for operation on Grade 80 avgas (or lower), UL91, or mogas. It is estimated that up to 65% of the fleet of current general aviation piston-engine-powered aircraft can operate on UL94 with no modifications to either the engine or airframe. Some aircraft, however, do require a [[Federal Aviation Administration|FAA]]-approved [[Supplemental type certificate|Supplemental Type Certificate]] (STC) to be purchased to allow for operation on UL94.<ref name="Swift Fuel product 94UL" /><ref>{{Cite web |url=https://swiftfuels.com/stc/|title=UL94 Supplemental Type Certificate|website=swiftfuels.com|access-date=April 14, 2017|archive-url=https://web.archive.org/web/20170415200555/https://swiftfuels.com/stc/|archive-date=April 15, 2017|url-status=dead}}</ref><ref>{{Cite web|title=FAA STC SA01757WI|website=rgl.faa.gov |url=http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgstc.nsf/0/E62733D88AD87BDE86257FBD0069CBA0?OpenDocument&Highlight=sa01757wi|access-date=April 14, 2017 |archive-date=April 15, 2017|archive-url=https://web.archive.org/web/20170415200917/http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgstc.nsf/0/E62733D88AD87BDE86257FBD0069CBA0?OpenDocument&Highlight=sa01757wi|url-status=live}}</ref>

UL94 has a minimum Motor octane number (MON, which is the [[octane rating]] employed for grading aviation gasoline) of 94.0. 100LL has a minimum MON of 99.6.<ref name="ASTM_D910" /><ref name=":0" />

AKI is the octane rating used to grade all U.S. automotive gasoline (typical values at the pump can include 87, 89, 91, and 93), and also the 93UL fuel from Airworthy AutoGas.

The minimum AKI of UL94, as sold by Swift Fuels, is 98.0.

Concurrent with the addition of UL94 to ASTM D7547, the FAA published Special Airworthiness Information Bulletin (SAIB) HQ-16-05, which states that "UL94 meets the operating limitations or aircraft and engines approved to operate with grade UL91 avgas," meaning that "Grade UL94 avgas that meets specification D7547 is acceptable to use on those aircraft and engines that are approved to operate with&nbsp;... grade UL91 avgas that meets specification D7547."<ref>{{Cite web|title=FAA SAIB HQ-16-05|date=November 10, 2015 |url=http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgSAIB.nsf/dc7bd4f27e5f107486257221005f069d/192e145c74199feb86257ef9006187bb/$FILE/HQ-16-05.pdf |website=rgl.faa.gov |access-date=April 14, 2017|archive-url=https://web.archive.org/web/20170125022626/http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgSAIB.nsf/dc7bd4f27e5f107486257221005f069d/192e145c74199feb86257ef9006187bb/$FILE/HQ-16-05.pdf|archive-date=January 25, 2017|url-status=live}}</ref> In August 2016, the FAA revised SAIB HQ-16-05 to include similar wording regarding the acceptability of using UL94 in aircraft and engines that are approved to operate with avgas that has a minimum Motor octane rating of 80 or lower, including Grade 80/87.<ref>{{Cite web |url=http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgSAIB.nsf/0/5efaf7b4e35481568625801f00642b6a/$FILE/HQ-16-05R1.pdf|title=FAA SAIB HQ-16-05R1 |date=August 30, 2016 |access-date=April 14, 2017|archive-url= https://web.archive.org/web/20170124195527/http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgSAIB.nsf/0/5efaf7b4e35481568625801f00642b6a/$FILE/HQ-16-05R1.pdf|archive-date=January 24, 2017 |url-status=live}}</ref>

The publication of the SAIB, especially the August 2016 revision, eliminated the need for many of the UL94 STCs being sold by Swift Fuels, as the majority of the aircraft on the STC's Approved Model List are type-certified to use 80-octane or lower avgas.

On April 6, 2017, Lycoming Engines published Service Instruction 1070V, which adds UL94 as an approved grade of fuel for dozens of engine models, 60% of which are carbureted engines. Engines with displacements of 235, 320, 360, and 540 cubic inches make up almost 90% of the models approved for UL94.<ref name="Lyc1070" />

===UL102 (formerly 100SF Swift Fuel)===
{{anchor|100SF Swift Fuel}}{{anchor |102UL}}[[File:Cessna150M-SwiftFuel.jpg|right|thumb|[[Purdue University]] [[Cessna 150M]] Swift Fuel demonstrator]]
Swift Fuels, LLC, has attained approval to produce fuel for testing at its pilot plant in Indiana. Composed of approximately 85% [[mesitylene]] and 15% [[isopentane]], the fuel is reportedly scheduled for extensive testing by the FAA to receive certification under the new ASTM D7719 guideline for unleaded 100LL replacement fuels. The company eventually intends to produce the fuel from renewable biomass feedstocks, and aims to produce something competitive in price with 100LL and currently available alternative fuels. Swift Fuels has suggested that the fuel, formerly referred to as 100SF, will be available for "high performance piston-powered aircraft" before 2020.<ref name="AOPA September 13, 2016 94UL"  />

John and Mary-Louise Rusek founded Swift Enterprises in 2001 to develop renewable fuels and hydrogen fuel cells. They began testing "Swift 142" in 2006<ref name=Delphi142test2006>{{cite news
|url=http://www.carrollcountycomet.com/news/2006/0621/front_page/002.html
|author=Jennifer Archibald
|title=Petroleum Free: New agriculture-based fuel revealed at Delphi Airport
|work=Carroll County Comet
|location=Flora, Indiana, USA
|date=June 21, 2006
|access-date=August 28, 2008
|archive-url=https://web.archive.org/web/20080810220613/http://www.carrollcountycomet.com/news/2006/0621/front_page/002.html
|archive-date=August 10, 2008
|url-status=dead
}}</ref> and patented several alternatives for non-alcohol based fuels which can be derived from [[biomass fermentation]].<ref name="SwiftPatent">The patent lists Mary-Louise Rusek and Jon Ziulkowski as inventors.{{Cite patent
 |country= US
 |number=2008168706
 |status=application
 |title= Renewable Engine Fuel
 |pubdate= July 17, 2008
 |fdate= 2007-07-27
 |invent1= Rusek, Mary-Louise, R
 |invent2= Ziulkowski, Jonathon, D.
 |assign1= Swift Enterprises, Ltd.
}}
{{Cite patent
|country=WO
|number=2008013922
|status=application
|title=Renewable Engine Fuel
|pubdate=2008-01-31
|fdate=2007-07-27
|pridate=27 July 2006
|invent1= Rusek, Mary-Louise, R
|invent2= Ziulkowski, Jonathon, D.
|assign1=Swift Enterprises Ltd
}}
</ref> Over the next several years, the company sought to build a pilot plant to produce enough fuel for larger-scale testing<ref name=CarrolCountyComet2007Nov7>{{cite news
|url=http://www.carrollcountycomet.com/news/2007/1107/local_news/033.html
|title=Permit required for tree activity in Delphi
|first=Debbie
|last=Lowe
|work=Carroll County Comet
|location=Flora, Indiana, USA
|date=November 7, 2007
|access-date=September 18, 2008
|archive-url=https://web.archive.org/web/20080719103651/http://www.carrollcountycomet.com/news/2007/1107/local_news/033.html
|archive-date=July 19, 2008
|url-status=dead
}}</ref><ref name=Delphishowcase>
{{cite news
 |author= Eric Weddle
 |title=Delphi could be showcase for renewable aviation fuel
 |url=http://www.jconline.com/apps/pbcs.dll/article?AID=/20080613/NEWS0501/806130330
 |work=Journal&Courrier
 |publisher=Federated Publisher Inc.
 |date=June 13, 2008
 |access-date=June 18, 2008}} {{Dead link|date=September 2010|bot=H3llBot}}
</ref> and submitted fuel to the FAA for testing.<ref name=MedillJune2008>
{{cite news
|url=http://news.medill.northwestern.edu/chicago/news.aspx?id=97989
|title=Swift Enterprises hopes to take off with renewable aviation gas
|publisher=Northwestern University Medill School of Journalism
|work=Medill Reports
|location=Chicago
|first=Sara
|last=Sargent
|date=August 26, 2008
|access-date=August 28, 2008
|archive-url=https://web.archive.org/web/20080904122727/http://news.medill.northwestern.edu/chicago/news.aspx?id=97989
|archive-date=September 4, 2008
|url-status=dead
}}</ref><ref name=NewAviationFuel>{{cite news
 |title=New Aviation Fuel Developed in Indiana 
 |url=http://www.insideindianabusiness.com/newsitem.asp?ID=29204 
 |work=Inside Indiana Business 
 |date=June 5, 2008 
 |access-date=June 18, 2008 
 |url-status=dead 
 |archive-url=https://web.archive.org/web/20110928195705/http://www.insideindianabusiness.com/newsitem.asp?ID=29204 
 |archive-date=September 28, 2011 
}}</ref><ref name=CarrollCountyCometJuly2008>{{cite news
|url=http://www.carrollcountycomet.com/news/2008/0730/local_news/054.html
|archive-url=https://archive.today/20130119094347/http://www.carrollcountycomet.com/news/2008/0730/local_news/054.html
|url-status=dead
|archive-date=January 19, 2013
|title=Demonstration fuel facility project accelerated
|first=Debbie
|last=Lowe
|work=Carroll County Comet
|location=Flora, Indiana, USA
|date=July 30, 2008
|access-date=August 28, 2008
}}</ref><ref name=CarrolCountyCometJuly92008>{{cite news
|url=http://www.carrollcountycomet.com/news/2008/0709/front_page/006.html
|archive-url=https://archive.today/20130118200159/http://www.carrollcountycomet.com/news/2008/0709/front_page/006.html
|url-status=dead
|archive-date=January 18, 2013
|title=Annual EDC request approved by Delphi
|first=Debbie
|last=Lowe
|work=Carroll County Comet
|location=Flora, Indiana, USA
|date=July 9, 2008
|access-date=September 18, 2008
}}</ref>

In 2008, an article by technology writer and aviation enthusiast [[Robert X. Cringely]] attracted popular attention to the fuel,<ref name="cringely">{{cite news
|title=It's the Platform, Stupid
|author=Robert X Cringely
|url=https://www.pbs.org/cringely/pulpit/2008/pulpit_20080606_005036.html
|publisher=PBS
|date=June 6, 2008
|access-date=August 24, 2017
|archive-date=August 21, 2016
|archive-url=https://web.archive.org/web/20160821210240/http://www.pbs.org/cringely/pulpit/2008/pulpit_20080606_005036.html
|url-status=dead
}}</ref> as also did a cross-country Swift-Fueled flight by the [[AOPA]]'s Dave Hirschman.<ref name=Hirschman>{{cite news
 |title=Grass for gas – Flying a real, renewable fuel 
 |author=Dave Hirschman 
 |url=http://www.aopa.org/members/files/pilot/2009/september/fuel0909.html
 |archive-url=https://archive.today/20130225030426/http://www.aopa.org/members/files/pilot/2009/september/fuel0909.html
 |url-status=dead
 |archive-date=February 25, 2013
 |publisher=AOPA 
 |date=September 3, 2009 
}}</ref> Swift Enterprises' claims that the fuel could eventually be manufactured much more cheaply than 100LL have been debated in the aviation press.<ref name="MedillJune2008"/><ref name="AvWeb03Mar09">{{cite web
|title= FAA Evaluates 100LL Alternative
|url= http://www.avweb.com/avwebbiz/news/FAAEvaluates100LLAlternative_199892-1.html
|access-date= March 5, 2009|last= Bertorelli |first= Paul |date=March 2009
|archive-url= https://web.archive.org/web/20090310002346/http://www.avweb.com/avwebbiz/news/FAAEvaluates100LLAlternative_199892-1.html
|archive-date= March 10, 2009 |url-status= live}}</ref><ref name="AvWeb08Mar09">{{cite web
|url= http://www.avweb.com/blogs/insider/AvWebInsider_SwifFuelRealities_199927-1.html
|title= Swift Fuel: Is It for Real?
|access-date= March 5, 2009|last= Bertorelli |first= Paul |date=March 2009
|archive-url= https://web.archive.org/web/20090312065452/http://www.avweb.com/blogs/insider/AvWebInsider_SwifFuelRealities_199927-1.html
|archive-date= March 12, 2009 |url-status= live}}</ref><ref name="Avweb07Feb10B">{{cite web
|url= http://www.avweb.com/avwebflash/exclusivevids/ExclusiveVideo_G100UL_FuelFlightTest_201983-1.html
|title= Exclusive Video: AVweb's G100UL Flight Test
|access-date= February 8, 2010|last= Bertorelli|first= Paul | date=February 2010 |archive-url= https://web.archive.org/web/20100213042707/http://www.avweb.com/avwebflash/exclusivevids/ExclusiveVideo_G100UL_FuelFlightTest_201983-1.html
|archive-date= February 13, 2010 |url-status= live}}</ref><ref name="AvWeb02May10">{{cite web
|url= http://www.avweb.com/blogs/insider/AvWebInsider_GulfDisaster_202481-1.html
|title= Oil Slicks and Avgas
|access-date= May 3, 2010|last= Bertorelli|first= Paul |date=May 2010
|archive-url= https://web.archive.org/web/20100507004156/http://www.avweb.com/blogs/insider/AvWebInsider_GulfDisaster_202481-1.html
|archive-date= May 7, 2010 |url-status= live}}</ref><ref name="ABS16Jun10">{{cite web
|url= http://www.bonanza.org/News/?id=583
|title= ABS Developing Fuels Strategy|access-date= June 19, 2010|last= The American Bonanza Society |date=June 2010
|archive-url= https://web.archive.org/web/20100625080954/http://www.bonanza.org/News/?id=583
|archive-date= June 25, 2010 |url-status= live}}</ref><ref name="AvWeb02Jul10">{{cite web
|url= http://www.avweb.com/avwebflash/news/SwiftFuelTiltsTowardNaturalGas_202814-1.html
|title= Swift Fuel: A Tilt Toward Natural Gas
|access-date= July 5, 2010
|last= Bertorelli
|first= Paul
|date= July 2010
|archive-date= July 7, 2010
|archive-url= https://web.archive.org/web/20100707084038/http://www.avweb.com/avwebflash/news/SwiftFuelTiltsTowardNaturalGas_202814-1.html
|url-status= live
}}</ref>

The FAA found Swift Fuel to have a [[motor octane number]] of 104.4, 96.3% of the energy per unit of mass, and 113% of the energy per unit of volume as 100LL, and to meet most of the ASTM D910 standard for leaded aviation fuel. Following tests in two Lycoming engines, the FAA concluded it performs better than 100LL in detonation testing and will provide a fuel saving of 8% per unit of volume, though it weighs {{convert|1|lb/USgal|g/L}} more than 100LL. [[Gas chromatograph|GC]]–[[flame ionization detector|FID]] testing showed the fuel to be made primarily of two components — one about 85% by weight and the other about 14% by weight.<ref name=AvWebFAAtest2008>{{cite news
|url=http://www.avweb.com/eletter/archives/bizav/1325-full.html#199892
|title=FAA Evaluates 100LL Alternative
|work=AvWeb
|volume=7
|number=9
|date=March 4, 2009
|last=Bertorelli
|first=Paul
|access-date=May 13, 2009
|archive-date=March 10, 2009
|archive-url=https://web.archive.org/web/20090310013536/http://www.avweb.com/eletter/archives/bizav/1325-full.html#199892
|url-status=live
}}</ref><ref name=FAAtest2008>{{cite web
|url=http://www.tc.faa.gov/its/worldpac/techrpt/ar0853.pdf
|title=DOT/FAA/AR-08/53 Full-Scale Engine Detonation and Power Performance Evaluation of Swift Enterprises 702 Fuel
|author=David Atwood
|publisher=[[FAA]] Office of Aviation Research and Development
|date=January 2009
|access-date=2009-05-13
|archive-date=2009-11-22
|archive-url=https://web.archive.org/web/20091122073037/http://www.tc.faa.gov/its/worldpac/techrpt/ar0853.pdf
|url-status=live
}}</ref> Soon afterward, AVweb reported that Continental had begun the process of certifying several of its engines to use the new fuel.<ref name=TCMtest>{{cite news 
 |url=http://www.avweb.com/news/snf/ContinentalBonanzaFliesOnSwiftFuel_200216-1.html 
 |title=Continental-powered Bonanza on Swift Fuel 
 |author=Russ Niles 
 |work=AVweb 
 |date=April 23, 2009 
 |access-date=May 13, 2009 
 |archive-date=June 12, 2011 
 |archive-url=https://web.archive.org/web/20110612022525/http://www.avweb.com/news/snf/ContinentalBonanzaFliesOnSwiftFuel_200216-1.html 
 |url-status=live 
 }} reporting on Press Release {{cite press release 
 |title=Continental Motors Completes First Flight on Unleaded AvGas 
 |url=http://tcmlink.com/pressReleases/UnleadedFuelFlight_Final.pdf 
 |publisher=Teledyne Continental Motors, Inc 
 |date=March 31, 2009 
 |quote=With the first flights complete, TCM will begin the certification process of several engine models to meet the needs for existing and future aircraft 
 |url-status=dead 
 |archive-url=https://web.archive.org/web/20090716093557/http://www.tcmlink.com/pressReleases/UnleadedFuelFlight_Final.pdf 
 |archive-date=July 16, 2009 
 }}</ref>

From 2009 through 2011, 100SF was approved as a test fuel by [[ASTM International]], allowing the company to pursue certification testing.<ref name="AvWeb15Dec09">{{cite web
|url= http://www.avweb.com/avwebflash/news/EffortsMoveForwardToProduceAlternativeAviationFuels_201691-1.html
|title= Efforts Move Forward To Produce Alternative Aviation Fuels
|access-date= March 5, 2009
|last= Grady
|first= Mary
|date= December 2009
|archive-date= June 12, 2011
|archive-url= https://web.archive.org/web/20110612031144/http://www.avweb.com/avwebflash/news/EffortsMoveForwardToProduceAlternativeAviationFuels_201691-1.html
|url-status= live
}}</ref><ref name="InsideIndiana15Dec09">{{cite web
 |url=http://www.insideindianabusiness.com/newsitem.asp?ID=39195#middle 
 |title=Indiana Airline Fuel Developer Moves Ahead With Testing 
 |access-date=December 17, 2009 
 |last=Purdue Research Park 
 |date=December 2009 
 |url-status=dead 
 |archive-url=https://web.archive.org/web/20110118042636/http://www.insideindianabusiness.com/newsitem.asp?ID=39195 
 |archive-date=January 18, 2011 
}}</ref> satisfactorily tested by the FAA,<ref name="AvWeb22Aug10">{{cite web
 |url          = http://www.avweb.com/avwebflash/news/Swift_Fuel_Engine_Test_Positive_203168-1.html
 |title        = Swift Fuel engine test results generally positive
 |access-date  = August 23, 2010
 |last         = Niles
 |first        = Russ
 |date         = August 2010
 |publisher    = Aviation Publishing Group
 |work         = Avweb
 |archive-date = June 11, 2011
 |archive-url  = https://web.archive.org/web/20110611230529/http://www.avweb.com/avwebflash/news/Swift_Fuel_Engine_Test_Positive_203168-1.html
 |url-status   = live
}}</ref> tested by Purdue University,<ref name="AvWeb27Oct10">{{cite news
|url= http://www.avweb.com/avwebflash/news/SwiftFuelExpandsTesting_203523-1.html
|title= Swift Fuel Expands Testing
|access-date= October 28, 2010|last= Grady|first= Mary |date=October 2010
|publisher=Aviation Publishing Group|work=Avweb
|archive-url= https://web.archive.org/web/20101101121151/http://www.avweb.com/avwebflash/news/SwiftFuelExpandsTesting_203523-1.html
|archive-date= November 1, 2010 |url-status= live}}</ref> and approved under ASTM specification D7719 for high-octane Grade UL102, allowing the company to test more economically in non-experimental aircraft.<ref name="GenAv20110525Swift">{{cite news
|url=http://www.generalaviationnews.com/2011/05/swiftfuel-meets-new-astm-standard/
|title=SwiftFuel meets new ASTM standard
|date=May 25, 2011
|work=General Aviation News
|access-date=September 27, 2013
|archive-date=October 2, 2013
|archive-url=https://web.archive.org/web/20131002191626/http://www.generalaviationnews.com/2011/05/swiftfuel-meets-new-astm-standard/
|url-status=live
}}</ref>

In 2012, Swift Fuels LLC was formed to bring in oil and gas industry experience, scale up production and bring the fuel to market. By November 2013, the company had built its pilot plant and received approval to produce fuel in it.<ref name="AOPASwiftPilotApproval">{{cite news
|url=http://www.aopa.org/News-and-Video/All-News/2013/November/11/swift-update.aspx
|title=Swift Fuels gains ASTM approval
|date=November 11, 2013
|author=Jim Moore
|publisher=Aircraft Owners and pilots Association
|access-date=December 12, 2013
|archive-date=November 18, 2013
|archive-url=https://web.archive.org/web/20131118142548/http://www.aopa.org/News-and-Video/All-News/2013/November/11/swift-update.aspx
|url-status=live
}}</ref> Its most recent patent, approved in 2013, describes methods by which the fuel can be produced from fermentable biomass.<ref name="SwiftPatent2013">{{Ref patent
 |country= US
 |number=8556999
 |status=patent
 |title= Renewable Engine Fuel and method of producing Same
 |pubdate= July 17, 2008
 |fdate= 2007-07-27
|invent1=RUSEK JOHN J
|invent2=RUSEK MARY-LOUISE R
|invent3=ZIULKOWSKI JONATHON D
|invent4=ZINK JUSTIN D
|assign1= Swift Enterprises LTD
}}</ref>

The FAA scheduled UL102 for 2 years of phase 2 testing in its PAFI initiative beginning in the summer of 2016.<ref name="AINOnline PAFI phase 2">{{cite news
|title=FAA Moves To Next Phase of Unleaded Avgas Testing
|url=https://www.ainonline.com/aviation-news/business-aviation/2016-03-30/faa-moves-next-phase-unleaded-avgas-testing
|work=AINOnline|publisher=Aviation International News
|last=Lynch|first=Kerry
|date=March 30, 2016
|access-date=February 13, 2017}}</ref>

===G100UL===
In February 2010, [[General Aviation Modifications Inc.]] (GAMI) announced that it was in the process of developing a 100LL replacement to be called G100UL ("unleaded"). This fuel is made by blending existing refinery products and yields detonation margins comparable to 100LL. The new fuel is slightly more dense than 100LL, but has a 3.5% higher thermodynamic output. G100UL is compatible with 100LL and can be mixed with it in aircraft tanks for use.<ref name="Avweb07Feb10B" /><ref name="gamimakes" /><ref name="Avweb07Feb10A">{{cite web
|url= http://www.avweb.com/avwebflash/news/AVwebFliesNewG100ULFuel_201982-1.html
|title= AVweb Flies New G100UL Fuel
|access-date= February 8, 2010
|last= Bertorelli
|first= Paul
|date= February 2010
|archive-date= February 21, 2010
|archive-url= https://web.archive.org/web/20100221224058/http://www.avweb.com/avwebflash/news/AVwebFliesNewG100ULFuel_201982-1.html
|url-status= live
}}</ref>

In demonstrations held in July 2010, G100UL performed better than 100LL that just meets the minimum specification and performed as well as average production 100LL.<ref name="Avweb08Jul10">{{cite web
|url= http://www.avweb.com/avwebflash/news/Pelton_Fuller_Look_At_G100UL_202845-1.html
|title= Pelton, Fuller Take A Look At GAMI's G100UL
|access-date= July 8, 2010
|last= Bertorelli
|first= Paul
|date= July 2010
|archive-date= June 11, 2011
|archive-url= https://web.archive.org/web/20110611225542/http://www.avweb.com/avwebflash/news/Pelton_Fuller_Look_At_G100UL_202845-1.html
|url-status= live
}}</ref>

G100UL was approved by the [[Federal Aviation Administration]] by the issuance of a [[Supplemental Type Certificate]] at [[AirVenture]] in July 2021. The STC was initially only applicable to Lycoming-powered models of the [[Cessna 172]]. The company indicated that the retail cost was expected to be 0.60–0.85 US dollars per US gallon higher than 100LL.<ref name="Bertorelli27Jul21"/> This was later revised to 1.00 US dollar per US gallon.<ref name="gamimakes"/>

In 2022, Paul Bertorelli of AVweb reported that the FAA was dragging its feet on broadly certifying G100UL, delaying approval of the fuel for more engines and spending over $80 million on EAGLE to re-start a search for an unleaded fuel when G100UL had been under evaluation for over 10 years.<ref name="Avweb05Apr22">{{cite web
|url=https://www.avweb.com/insider/faa-do-your-damn-job/
|title=FAA, Do Your Damn Job
|last= Bertorelli
|first= Paul
|date= April 5, 2022
|publisher= Avweb
|access-date= April 7, 2022
}}</ref>

In September 2022, in a surprise announcement, the FAA approved an STC for the use of the fuel for all piston-engined aircraft and engine combinations. In February 2023, GAMI began selling supplemental type certificates to allow aircraft owners to use the fuel when it becomes available.<ref name="O'Connor01Sep22">{{cite web|url= https://www.avweb.com/ownership/fuel-news/gami-unleaded-avgas-stcs-approved-for-ga-piston-fleet/|title= GAMI Unleaded Avgas Approved For GA Piston Fleet|access-date= 3 September 2022|last= O'Connor|first= Kate|work= AVweb|date= 1 September 2022|archive-url= https://archive.today/20220903002713/https://www.avweb.com/ownership/fuel-news/gami-unleaded-avgas-stcs-approved-for-ga-piston-fleet/|archive-date= 3 September 2022|url-status= live}}</ref><ref name="O'Connor02Feb23">{{cite web|url= https://www.avweb.com/ownership/fuel-news/gami-begins-g100ul-stc-sales/|title= GAMI Begins G100UL STC Sales|access-date= 3 February 2023|last= O'Connor|first= Kate |work= AVweb|date= 2 February 2023|archive-url= https://archive.today/20230203124930/https://www.avweb.com/ownership/fuel-news/gami-begins-g100ul-stc-sales/|archive-date= 3 February 2023|url-status= live}}</ref> In April 2024, GAMI announced that 1 million gallons of G100UL had been produced. Fuel availability in the US was forecast for airports in California, Washington and Oregon by the middle of 2024 and the rest of the country by 2026.<ref name ="onemillion"/><ref name ="gamimakes"/><ref name="O'Connor01Sep22"/><ref name="O'Connor02Feb23"/>

In December 2024, shortly after G100UL was made available at selected airports in California, several concerns regarding material compatibility arose, as users reported fuel leaks, paint staining, and paint stripping.<ref>{{cite web
|url= https://www.avweb.com/aviation-news/california-mechanics-tests-show-g100ul-paint-nitrile-o-ring-damage-under-some-circumstances/
|title= AVweb G100UL YouTuber Tests
|date= December 24, 2024
}}</ref>

===Shell Unleaded 100-Octane Fuel===
In December 2013, [[Shell Oil]] announced that they had developed an unleaded 100 octane fuel and will submit it for FAA testing with certification expected within two to three years.<ref>{{cite web |last=Bertorelli |first=Paul |url=http://www.avweb.com/avwebflash/news/Shell-Announces-Unleaded-100-Octane-Fuel221070-1.html |title=Shell Announces Unleaded 100-Octane Fuel |publisher=Avweb |date=December 3, 2013 |access-date=December 3, 2013 |url-status=live |archive-date=December 9, 2013 |archive-url=https://web.archive.org/web/20131209125123/http://www.avweb.com/avwebflash/news/Shell-Announces-Unleaded-100-Octane-Fuel221070-1.html}}</ref> The fuel is alkylate-based with an additive package of aromatics. No information has yet been published with regard to its performance, producibility or price. Industry analysts have indicated that it will likely cost as much as or more than existing 100LL.<ref>{{cite web |last=Bertorelli |first=Paul |url=http://www.avweb.com/blogs/insider/Shells-New-Avgas-Inside-Comments-221106-1.html |title=Shell's New Avgas: Inside Comments |publisher=Avweb |date=December 11, 2013 |archive-url=https://web.archive.org/web/20140814213010/http://www.avweb.com/blogs/insider/Shells-New-Avgas-Inside-Comments-221106-1.html |archive-date=August 14, 2014 |url-status=live |access-date=December 12, 2013}}</ref>

===UL100E===
In 2018, [[LyondellBasell]] and VP Racing Fuels, an established motorsport fuel manufacturer, announced its intention to participate in developing an unleaded fuel for piston-powered aircraft.  As of December 2024, it has reached Phase 4 of testing, according to the FAA.<ref>{{Cite web |title=PAFI Unleaded Fuel Testing Protocols – UL100E as of 9-Dec-2024 |url=https://flyeagle.org/wp-content/uploads/2024/12/PAFI-Update.pdf |archive-url=https://web.archive.org/web/20250114023335/https://flyeagle.org/wp-content/uploads/2024/12/PAFI-Update.pdf |archive-date=2025-01-14 |website=flyeagle.org}}</ref>

==Environmental regulation==
TEL found in leaded avgas and its combustion products are potent [[neurotoxin]]s that have been shown in scientific research to interfere with brain development in children. Children in residences or childcare facilities in close proximity to airports with moderate to high piston engine aircraft traffic are at especially high risk of high blood lead levels.<ref>{{cite web |title=National Analysis of the Populations Residing Near or Attending School Near U.S. Airports – February 2020 Final Report |publisher=United States Environmental Protection Agency |url=https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P100YG4A.pdf |access-date=5 May 2022}}</ref><ref>{{cite journal |last1=Zahran |first1=Sammy |last2=Iverson |first2=Terrence |last3=McElmurry |first3=Shawn P. |last4=Weiler |first4=Stephan |title=The Effect of Leaded Aviation Gasoline on Blood Lead in Children |journal=Journal of the Association of Environmental and Resource Economists |date=1 June 2017 |volume=4 |issue=2 |pages=575–610 |doi=10.1086/691686|s2cid=59126623 }}</ref><ref>{{cite journal |last1=Miranda |first1=Marie Lynn |last2=Anthopolos |first2=Rebecca |last3=Hastings |first3=Douglas |title=A Geospatial Analysis of the Effects of Aviation Gasoline on Childhood Blood Lead Levels |journal=Environmental Health Perspectives |date=1 October 2011 |volume=119 |issue=10 |pages=1513–1516 |doi=10.1289/ehp.1003231|pmid=21749964 |pmc=3230438 |bibcode=2011EnvHP.119.1513M }}</ref> The [[United States Environmental Protection Agency]] (EPA) has noted that exposure to even very low levels of lead contamination has been conclusively linked to loss of [[Intelligence quotient|IQ]] in children's brain function tests, thus providing a high degree of motivation to eliminate lead and its compounds from the environment.<ref name="AvWeb20081016">{{cite web
|url= http://www.avweb.com/avwebflash/news/epa_100ll_lead_standard_aviation_fuel_199020-1.html
|title= EPA Sets New Standard For Lead In Air
|access-date= October 20, 2008
|last= Pew
|first= Glenn
|date= October 2008
|archive-date= January 25, 2022
|archive-url= https://web.archive.org/web/20220125022025/https://www.avweb.com/news/epa-sets-new-standard-for-lead-in-air/
|url-status= live
}}</ref><ref name="MarketWatch_WHO">{{cite news
 |publisher    = MarketWatch.com
 |url          = https://www.who.int/ceh/publications/leadguidance.pdf
 |title        = New EPA lead standard significantly improved to protect kids' health
 |access-date  = October 20, 2008
 |last         = Balbus
 |first        = John
 |date         = October 2008
 |archive-date = February 6, 2011
 |archive-url  = https://web.archive.org/web/20110206182131/http://www.who.int/ceh/publications/leadguidance.pdf
 |url-status   = live
}}</ref>

{{cquote|While lead concentrations in the air have declined, scientific studies have demonstrated that children's neurological development is harmed by much lower levels of lead exposure than previously understood. Low level lead exposure has been clearly linked to loss of IQ in performance testing. Even an average IQ loss of 1–2 points in children has a meaningful impact for the nation as a whole, as it would result in an increase in children classified as mentally challenged, as well as a proportional decrease in the number of children considered "gifted".<ref name="MarketWatch_WHO" />}}

On November 16, 2007, the [[environmentalism|environmental group]] [[Friends of the Earth]] formally petitioned the EPA, asking them to regulate leaded avgas. The EPA responded with a notice of petition for rulemaking.<ref name="AvWeb20071117"/>

The notice of petition stated:

{{cquote|Friends of the Earth has filed a petition with EPA, requesting that EPA find pursuant to section 231 of the [[Clean Air Act (United States)|Clean Air Act]] that lead emissions from general aviation aircraft cause or contribute to air pollution that may reasonably be anticipated to endanger public health or welfare and that EPA propose emissions standards for lead from general aviation aircraft. Alternatively, Friends of the Earth requests that EPA commence a study and investigation of the health and environmental impacts of lead emissions from general aviation aircraft, if EPA believes that insufficient information exists to make such a finding. The petition submitted by Friends of the Earth explains their view that lead emissions from general aviation aircraft endanger the public health and welfare, creating a duty for the EPA to propose emission standards.<ref name="FederalRegister16Nov07"/> }}

The public comment period on this petition closed on March 17, 2008.<ref name="FederalRegister16Nov07">{{cite web
 |url=http://a257.g.akamaitech.net/7/257/2422/01jan20071800/edocket.access.gpo.gov/2007/E7-22456.htm 
 |title=Federal Register: November 16, 2007 (Volume 72, Number 221) 
 |access-date=February 24, 2008 
 |last=Environmental Protection Agency 
 |date=November 2007 
 |url-status=dead 
 |archive-url=https://web.archive.org/web/20080725191333/http://a257.g.akamaitech.net/7/257/2422/01jan20071800/edocket.access.gpo.gov/2007/E7-22456.htm 
 |archive-date=July 25, 2008 
}}</ref>

Under a federal court order to set a new standard by October 15, 2008, the EPA cut the acceptable limits for atmospheric lead from the previous standard of 1.5&nbsp;μg/m<sup>3</sup> to 0.15&nbsp;μg/m<sup>3</sup>. This was the first change to the standard since 1978 and represents an order of magnitude reduction over previous levels. The new standard requires the 16,000 remaining USA sources of lead, which include lead smelting, airplane fuels, military installations, mining and metal smelting, iron and steel manufacturing, industrial boilers and process heaters, hazardous waste incineration, and production of batteries, to reduce their emissions by October 2011.<ref name="AvWeb20081016" /><ref name="MarketWatch_WHO" /><ref name="CBC20081016">{{cite news
|url= https://www.cbc.ca/news/science/u-s-tightens-health-standard-for-airborne-lead-1.773415
|title= U.S. tightens health standard for airborne lead
|access-date= October 17, 2008
|last= [[Canadian Broadcasting Corporation]]
|date= October 2008
|work= CBC News
|archive-date= February 8, 2009
|archive-url= https://web.archive.org/web/20090208222904/http://www.cbc.ca/health/story/2008/10/16/lead-air.html
|url-status= live
}}</ref>

The EPA's own studies have shown that to prevent a measurable decrease in IQ for children deemed most vulnerable, the standard needs to be set much lower, to 0.02&nbsp;μg/m<sup>3</sup>. The EPA identified avgas as one of the most "significant sources of lead".<ref>{{Cite web|url=https://journalistsresource.org/environment/plane-lead-fuel-emissions-economic-impact/|title=Lead emissions from planes may be costing billions in lost earnings|date=December 16, 2016|access-date=December 31, 2021|archive-date=December 31, 2021|archive-url=https://web.archive.org/web/20211231165720/https://journalistsresource.org/environment/plane-lead-fuel-emissions-economic-impact/|url-status=live}}</ref><ref>{{Cite web|url=http://icooolps.info/astm-d910-11/|title=ASTM D910 PDF|date=October 7, 2019|access-date=December 31, 2021|archive-date=January 19, 2021|archive-url=https://web.archive.org/web/20210119182648/https://icooolps.info/astm-d910-11/|url-status=usurped}}</ref>

At an EPA public consultation held in June 2008 on the new standards, Andy Cebula, the [[Aircraft Owners and Pilots Association]]'s executive vice president of government affairs, stated that [[general aviation]] plays a valuable role in the USA economy and any changes in lead standards that would change the current composition of avgas would have a "direct impact on the safety of flight and the very future of light aircraft in this country".<ref name="AOPA1">{{cite web|url= http://www.aopa.org/advocacy/articles/2008/081017epa.html|title= EPA sets new air quality standard|access-date= October 20, 2008|last= Hirschman|first= Dave|date= October 2008|archive-url= https://web.archive.org/web/20081027085218/http://www.aopa.org/advocacy/articles/2008/081017epa.html|archive-date= October 27, 2008|url-status= dead}}</ref>

In December 2008, [[Aircraft Owners and Pilots Association|AOPA]] filed formal comments to the new EPA regulations. AOPA has asked the EPA to account for the cost and the safety issues involved with removing lead from avgas. They cited that the aviation sector employs more than 1.3 million people in the US and has an economic direct and indirect effect that "exceeds $150 billion annually". AOPA interprets the new regulations as not affecting general aviation as they are currently written.<ref name="AvWeb20081205">{{cite web
|url= http://www.avweb.com/avwebflash/news/lead_fuel_emissions_air_epa_aopa_aviation_199344-1.html
|title= Leaded Fuel, Emissions, The EPA And AOPA
|access-date= December 8, 2008
|last= Pew
|first= Glenn
|date= December 5, 2008
|archive-date= February 8, 2009
|archive-url= https://web.archive.org/web/20090208231042/http://www.avweb.com/avwebflash/news/lead_fuel_emissions_air_epa_aopa_aviation_199344-1.html
|url-status= live
}}</ref>

Publication in the USA [[Federal Register]] of an Advance Notice of Proposed Rulemaking by the USA EPA occurred in April 2010. The EPA indicated: "This action will describe the lead inventory related to use of leaded avgas, air quality and exposure information, additional information the Agency is collecting related to the impact of lead emissions from piston-engine aircraft on air quality and will request comments on this information."<ref name="AvWeb20070410">{{cite web
|url= http://www.avweb.com/avwebflash/news/LeadedAvgasIssueMovingToFrontBurner_202299-1.html
|title= Leaded Avgas Issue Moving To Front Burner
|access-date= April 8, 2010
|last= Grady
|first= Mary
|date= April 10, 2007
|archive-date= June 11, 2011
|archive-url= https://web.archive.org/web/20110611222926/http://www.avweb.com/avwebflash/news/LeadedAvgasIssueMovingToFrontBurner_202299-1.html
|url-status= live
}}</ref><ref name="AvWeb20100410">{{cite web
|url= http://www.avweb.com/avwebflash/news/EPAAdvances100LLRulemakingProcess_202434-1.html
|title= EPA Advances 100LL Rulemaking Process
|access-date= April 22, 2010
|last= Grady
|first= Mary
|date= April 10, 2010
|archive-date= August 11, 2010
|archive-url= https://web.archive.org/web/20100811105412/http://www.avweb.com/avwebflash/news/EPAAdvances100LLRulemakingProcess_202434-1.html
|url-status= live
}}</ref>

Despite assertions in the media that leaded avgas will be eliminated in the US by 2017 at the latest date, the EPA confirmed in July 2010 that there is no phase-out date and that setting one would be an FAA responsibility as the EPA has no authority over avgas. The FAA administrator stated that regulating lead in avgas is an EPA responsibility, resulting in widespread criticism of both organizations for causing confusion and delaying solutions.<ref name="AvWeb20100704">{{cite web|url=http://www.avweb.com/blogs/insider/AVwebInsider_FuelFight_202818-1.html|title=Fuel Fight: It's About Time|access-date=July 5, 2010|last=Bertorelli|first=Paul|date=July 4, 2010|archive-url=https://web.archive.org/web/20100710080511/http://www.avweb.com/blogs/insider/AVwebInsider_FuelFight_202818-1.html|archive-date=July 10, 2010|url-status=live}}</ref><ref name="AvWeb20100728A">{{cite web |url=http://www.avweb.com/news/airventure/EAAAirVenture2010_EPA_Says_No_Deadline_On_Lead_In_Fuel_202974-1.html|title=EPA On Lead In Fuel: No Immediate Deadline|access-date=July 28, 2010|last=Bertorelli|first=Paul|date=July 28, 2010 |archive-date=June 11, 2011|archive-url=https://web.archive.org/web/20110611225733/http://www.avweb.com/news/airventure/EAAAirVenture2010_EPA_Says_No_Deadline_On_Lead_In_Fuel_202974-1.html|url-status=live}}</ref><ref name="AvWeb20100728B">{{cite web|url=http://www.avweb.com/news/airventure/EAAAirVenture2010_100LLReplacement_DontPanic_202973-1.html|title=Industry Leaders: Don't Panic On Avgas|access-date=July 28, 2010 |last=Bertorelli |first=Paul|date=July 28, 2010|archive-date=June 11, 2011|archive-url=https://web.archive.org/web/20110611225807/http://www.avweb.com/news/airventure/EAAAirVenture2010_100LLReplacement_DontPanic_202973-1.html |url-status=live}}</ref><ref name="AvWeb20100728C">{{cite web|url=http://www.avweb.com/blogs/insider/AVWebInsider_EPAConflict_203002-1.html|title=AirVenture 2010: Avgas — Top 'er off with 100 gallons of muddled message|access-date=July 29, 2010 |last=Bertorelli|first=Paul|date=July 28, 2010|archive-date=June 11, 2011|archive-url=https://web.archive.org/web/20110611225813/http://www.avweb.com/blogs/insider/AVWebInsider_EPAConflict_203002-1.html|url-status=live}}</ref><ref name="AvWeb20100728D">{{cite web|url=http://www.avweb.com/news/airventure/babbitt_contradict_epa_lead_gas_tetraethyl_alternative_202992-1.html|title=100LL: FAA's Babbitt contradicts EPA statement|access-date=July 29, 2010 |last=Pew|first=Glenn|date=July 28, 2010|archive-date=June 11, 2011|archive-url=https://web.archive.org/web/20110611225953/http://www.avweb.com/news/airventure/babbitt_contradict_epa_lead_gas_tetraethyl_alternative_202992-1.html |url-status=live}}</ref>

In April 2011 at [[Sun 'n Fun]], Pete Bunce, head of the [[General Aviation Manufacturers Association]] (GAMA), and Craig Fuller, president and CEO of the [[Aircraft Owners and Pilots Association]], indicated that they both are confident that leaded avgas will not be eliminated until a suitable replacement is in place. "There is no reason to believe 100 low-lead will become unavailable in the foreseeable future," Fuller stated.<ref name="AvWeb02Apr11">{{Cite news|title="Town Meeting" Issues: Avgas, Pilot Decline |url=http://www.avweb.com/news/snf/SunNFun2011_TownMeetingIssues_AvgasPilotDecline_204404-1.html|access-date=April 3, 2011|last=Grady|first=Mary|date=April 2011 |work=AvWeb|archive-date=January 25, 2012|archive-url=https://web.archive.org/web/20120125213322/http://www.avweb.com/news/snf/SunNFun2011_TownMeetingIssues_AvgasPilotDecline_204404-1.html|url-status=live}}</ref>

Final results from EPA's lead modeling study at the Santa Monica Airport shows off-airport levels below current 150&nbsp;ng/m<sup>3</sup> and possible future 20&nbsp;ng/m<sup>3</sup> levels.<ref>{{cite web |url=http://www.smgov.net/uploadedFiles/Departments/Airport/CommissionMeetings/EPA%20Lead%20Modeling%20Study%20Presentation.pdf|title=Final Results from EPA's Lead Modeling Study at the Santa Monica Airport, by Arnold Den, Senior Science Advisor, February 22, 2010|website=smgov.net|access-date=August 27, 2018|archive-url=https://web.archive.org/web/20170703054931/https://www.smgov.net/uploadedFiles/Departments/Airport/CommissionMeetings/EPA%20Lead%20Modeling%20Study%20Presentation.pdf|archive-date=July 3, 2017|url-status=live}}</ref> Fifteen of 17 airports monitored during a year-long study in the US by the EPA have lead emissions well below the current National Ambient Air Quality Standard (NAAQS) for lead.<ref name=AOPA20130620>{{cite web|title=GA community works to replace 100LL|publisher=Aircraft Owners and Pilots Association |url=http://www.aopa.org/News-and-Video/All-News/2013/June/20/ga-community-works-to-replace-100ll.aspx |access-date=June 23, 2013|date=June 20, 2013|quote="15 of the [17] airports monitored during a year-long study have lead emissions well below the current National Ambient Air Quality Standard (NAAQS) for lead." |archive-date=June 25, 2013|archive-url=https://web.archive.org/web/20130625013907/http://www.aopa.org/News-and-Video/All-News/2013/June/20/ga-community-works-to-replace-100ll.aspx|url-status=live}}</ref>

==Other uses==
Avgas is occasionally used in [[auto racing|amateur auto racing]] cars as its octane rating is higher than automotive gasoline thus allowing the engines to run at higher compression ratios.{{citation needed|date=October 2013}}

==See also==
*{{annotated link|Greenhouse gas emissions#By type of energy source|Greenhouse gas emissions § By type of energy source}}

== Notes ==
{{notelist}}

==References==
{{Reflist|30em}}

==External links==
*[https://skyfuel.ch/] AVGAS

[[Category:Aviation fuels]]