View source for Avgas

{{Infobox aviation
|name=Avgas
|image=Image:AmericanAviationAA-1YankeeC-FBVQrefueling01.jpg
|caption=An [[Grumman American AA-1|American Aviation AA-1 Yankee]] being refueled with 100LL avgas.
}}

'''Avgas''' ('''av'''iation '''gas'''oline), also known as ''aviation spirit'' in the [[United Kingdom|UK]], is an [[aviation fuel]] used in spark-ignited internal-combustion engines to propel aircraft. ''Avgas'' is distinguished from ''mogas'' (motor [[gasoline]]), which is the everyday gasoline used in [[motor vehicle]]s and some light aircraft. Unlike mogas, which has been formulated since the 1970s to allow the use of [[platinum]]-content [[catalytic converter]]s for pollution reduction, some grades of avgas still contain [[tetraethyllead]] (TEL), a toxic substance used to prevent [[engine knocking]] (detonation), with ongoing experiments aimed at eventually reducing or eliminating the use of TEL in aviation gasoline.

[[Gas turbine|Turbine]] and [[aircraft Diesel engine|diesel engines]] are designed to use [[kerosene]]-based [[jet fuel]].

==Properties==
The main [[petroleum]] component used in blending avgas is [[alkylate]], which is essentially a mixture of various [[2,2,4-Trimethylpentane|isooctanes.]] Some refineries also use [[reformate]]. All grades of avgas that meet CAN 2-3, 25-M82 have a [[density]] of 6.01&nbsp;lb/[[US gallon|U.S. gal]] at 15&nbsp;°C, or 0.721&nbsp;kg/l. (6&nbsp;lb/U.S. gal is commonly used 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 6.41&nbsp;lb/US gallon, or 0.769&nbsp;kg/l, at -40&nbsp;°C, and decreases by about 0.1% per 1C° (1.8F°) 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
 |origyear= 1941
 |edition= Millennium
 |year=2004
 |publisher= Aviation Publishers Co. Limited
 |location= Ottawa, Ontario, Canada
 |isbn= 0-9680390-5-7
 |pages= 265, 261
 |chapter= Chapter 10. Airmanship
}}</ref>
<ref name="CFS">[[Nav Canada]]: ''[[Canada Flight Supplement]]'', page A40. Nav Canada, 23 November 2006</ref>
Avgas has an [[emission factor|emission coefficient]] (or factor) of 18.355 pounds {{CO2|link=yes}} per U.S. gallon (2.1994&nbsp;kg/l)<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 |accessdate= 2007-12-03
|archiveurl= http://web.archive.org/web/20080303154810/http://www.eia.doe.gov/oiaf/1605/factors.html
|archivedate= 2008-03-03}}</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 |accessdate= 2007-12-03
}}</ref> or about 3.05 units of weight {{Carbon}}{{Oxygen}}<sub>2</sub> produced per unit weight of fuel used. Avgas has a lower and more uniform [[vapor pressure]] than automotive gasoline so it remains in the liquid state despite the reduced atmospheric pressure at high altitude, thus preventing [[vapor lock]].{{Citation needed|date=July 2013}}

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 US-made liquid-cooled [[Allison V-1710]] engines, and numerous radial engines from Pratt & Whitney, Wright, and other manufacturers on both sides of the Atlantic. The high octane ratings are achieved by the addition of TEL, a highly toxic substance that was [[Tetraethyllead#Phaseout and ban|phased out of automotive use in most countries]] in the late 20th century.{{Citation needed|date=July 2013}}

Avgas is currently available in several grades with differing maximum lead concentrations. Because TEL is an expensive and polluting ingredient, 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; a suitable unleaded replacement fuel has not yet been developed and certified for most of these engines. {{As of|2013}}, numerous certificated reciprocating-engine aircraft require high-octane (leaded) fuels. Teledyne-Continental Motors states: ''"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. The result can be remarkable, with cylinder performance deteriorating to unacceptable levels in under 10 hours."'' <ref>{{cite web|title=USE OF AUTOMOTIVE GASOLINE IN TCM AIRCRAFT ENGINES|url=http://www.tcmlink.com/visitors/carenfeed/engoperhdr.cfm|website=Teledyne Continental Motors|publisher=Teledyne Continental Motors|accessdate=22 May 2015}}</ref> Lycoming has also provided a list of engines and fuels that are compatible with them. A number of their engines are not compatible with unleaded fuel according to their chart.<ref>{{cite web|title=Specified Fuels for Spark Ignited Gasoline Aircraft Engine Models|url=http://www.lycoming.com/Portals/0/Upload/SI1070S%20Specified%20Fuels.pdf|website=Lycoming|publisher=Lycoming|accessdate=22 May 2015}}</ref>

[[Jet fuel]] is similar to [[kerosene]] and is used in turbine engines; it is not avgas. Confusion can be caused by the terms Avtur and AvJet being used for jet fuel. In Europe, environmental and cost considerations have led to increasing numbers of aircraft being fitted with fuel-efficient diesel engines that run on jet fuel. Civilian aircraft use [[Jet-A]], [[Jet-A1]], or in severely cold climates [[Jet-B]]. There are other classification systems for military turbine and diesel fuel.

==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}}</ref>

{{As of|2008}}, the main consumers of avgas are in [[North America]], [[Australia]], [[Brazil]], and [[Africa]] (mainly [[South Africa]]). Care must be taken by small airplane pilots to select airports with avgas on flight planning. For example, US and Japanese recreational pilots ship and depot avgas before flying into [[Siberia]]. Shrinking availability of avgas drives usage of small airplane engines that can use jet fuel.{{Citation needed|date=July 2013}}

In [[Europe]], avgas remains the most common fuel; prices are so high that there have been efforts to convert to [[diesel fuel]] which is common, inexpensive, and has advantages for aviation use.{{Citation needed|date=July 2013}}

==Grades==
Many 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
|accessdate= 2011-11-18
|publisher=AV Web|date=April 2002 }}</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)|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">Aviation Publishers Co. Limited, ''From the Ground Up'' (20th revised edition), page 20, ISBN 0-9690054-2-3</ref>

Additives such as TEL help to control detonation and provide lubrication. One gram of TEL contains 640.6 milligrams of {{lead}}.

{| 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 {{nowrap|("avgas 80")}}
| red<br/>{{nowrap|(red + a little blue)}}
| 0.14
| TEL
| It was used in engines with low [[compression ratio]].
| Phased out in the late 20th century. Its availability is very limited.{{Citation needed|date=July 2011}}
|-
| 82UL
| purple<br/>{{nowrap|(red + blue)}}
| 0
| ASTM D6227; similar to automobile gasoline but without automotive additives
| {{As of|2008}}, 82UL is not being produced and no refiner has announced plans to put it into production.<ref name="ShellAvgasSpecs" /><ref name="AvWeb20071117">{{cite web|url= http://www.avweb.com/avwebflash/news/GroupAsksEPAToGetTheLeadOutOfAvgas_196596-1.html|title= Avgas: Group Asks EPA To Get The Lead Out|accessdate= 2008-02-18|last=Pew|first= Glenn|date=November 2007|archiveurl= http://web.archive.org/web/20080224152525/http://www.avweb.com/avwebflash/news/GroupAsksEPAToGetTheLeadOutOfAvgas_196596-1.html|archivedate= 24 February 2008|deadurl= no}}</ref>
|
|-
| 85UL
| none
| 0
| oxygenate-free
|Used to power piston-engine ultralight aircraft.<br/>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|accessdate=2013-05-22}}</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/>{{nowrap|(orange + blue + red)}}
| almost negligible
| TEL
| Made particularly for military use.
|
|-
| 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 |accessdate=2013-05-21}}</ref> ASTM D7547
| In 1991, Hjelmco Oil introduced unleaded avgas 91/96UL (also meeting leaded grade 91/98 standard ASTM D910 with the exception of transparent colour) and no lead {{Citation needed|date=February 2010}} in Sweden. Engine manufacturers Teledyne Continental Motors, Textron Lycoming, Rotax, and radial engine manufacturer [[PZL#WSK "PZL-Kalisz"|Kalisz]] have cleared the Hjelmco avgas 91/96UL which in practice means that 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|accessdate= 31 October 2010|last= [[Rotax]] |date=April 2009}}</ref><ref name="Teledyne24Jan91">{{cite web|title= Teledyne Continental Letter|url= http://www.hjelmco.com/upl/files/2911.pdf|accessdate= 2010-02-13|last= Wheelock|first= Jim |year=1991|month=January}}</ref><ref name="Lycoming 16April12">{{cite web|title= Lycoming Service Instruction 1070R|url= http://www.lycoming.com/support/publications/service-instructions/pdfs/SI1070R.pdf|accessdate= 2012-05-17|last= Lycoming |date=April 2012}}</ref><ref name="Kalisz30Oct06">{{cite web|title= Service Bulletin 129/S/2006|url= http://www.hjelmco.com/upl/files/37123.pdf|accessdate= 2010-02-13|last= Miring|first= Robert |date=October 2006}}</ref> May be used in [[Rotax]] engines,<ref>{{cite web|url=http://www.lightaircraftassociation.co.uk/2011/unleaded%20AAN.pdf|title=Rotax Instruction|publisher= lightaircraftassociation.co.uk|year=2011 |accessdate=2013-05-22}}</ref> and Lycoming engines per SI1070R.<ref>{{cite web|url=http://www.lycoming.com/support/publications/service-instructions/pdfs/SI1070R.pdf|title=Lycoming Service Instruction |publisher=Lycoming.com |accessdate=2013-05-21}}</ref>
| In November 2010, the European Aviation Safety Agency (EASA) based on about 20 years of trouble-free operations with unleaded avgas 91/96UL produced by Hjelmco Oil cleared this fuel for all aircraft where the aircraft engine manufacturer has approved this fuel.<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=8 November 2010|accessdate=6 November 2012}}</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 |accessdate=2013-05-21}}</ref>
| Specially formulated for [[Shvetsov ASh-62]] and [[Ivchenko AI-14]] – nine-cylinder, air-cooled, radial aircraft engines.
| [[The Commonwealth of Independent States]], produced exclusively by OBR PR.

|-
| 100LL
| blue
| 0.56 g/l<ref name=ASTM_D910>{{cite web|title=ASTM D910|url=http://www.astm.org/Standards/D910.htm|publisher=ASTM International|accessdate=6 March 2015|location=West Conshohocken, PA, USA}}</ref>
| TEL<br/>{{As of|2010|1}}, 100LL has 1.2 to {{nowrap|2 grams}} TEL<ref name="EAASpecs">{{cite web |url= http://www.eaa.org/autofuel/avgas/avgas_specs.asp|title= Avgas Specifications|accessdate= 2009-11-30|publisher=[[Experimental Aircraft Association]]|year=2009}}</ref> per US gallon.
| Most commonly used aviation gasoline.
| Pretty much worldwide

|-
| 100/130
| green<br/>{{nowrap|(yellow + blue)}}
| 1.12
| TEL
| Mostly replaced by 100LL.
| {{As of|2013|8}}, [[Australia]], [[New Zealand]], [[Chile]], and the states of [[Hawaii]] and [[Utah]] in the [[United States]].

|-
| G100UL
| none
| 0
| aromatic compounds such as xylene or [[mesitylene]]
| Composed primarily of aviation alkylate (same as used for 100LL).
| {{As of|2013|8}}, limited quantities are produced for testing.

|-
| 100SF
| none
| 0
| mesitylene
| Swift Fuel LLC blend of 83% [[mesitylene]], 17% [[isopentane]]
| Limited quantities are produced for testing.

|-
| 115/145 {{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= 24 January 1978|accessdate=6 March 2015|publisher=United States military}}</ref>
| TEL
| Originally used as primary fuel for 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= 2010-09-30|author=VP Fuels}}</ref>
| Limited batches are produced for special events such as unlimited air races.

|}

===100LL (blue)===
[[Image: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 is pronounced "one hundred low lead". It may contain a maximum of one-half the TEL allowed in 100/130 (green) avgas and pre-1975 premium leaded automotive gasoline.<ref name=ASTM_D910>{{cite web|title=ASTM D910|url=http://www.astm.org/Standards/D910.htm|publisher=ASTM International|accessdate=6 March 2015|location=West Conshohocken, PA, USA}}</ref><ref name="The Rise and Fall of Tetraethyllead">{{cite web|title=The Rise and Fall of Tetraethyllead|url=http://pubs.acs.org/doi/pdf/10.1021/om030621b|accessdate=6 March 2015|location=Washington, D.C., USA}}</ref>

Many Continental and Lycoming light airplane engines designed for 80/87 remain in production. Engines designed for 80/87 and not for 100LL might have lead buildup and lead fouling of the spark plugs if 100LL is used.{{Citation needed|date=July 2011}}

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===

[[Image:EAA150.jpg|right|thumb|An EAA Cessna 150 used for American STC certification of auto fuel]]
Automotive [[gasoline]]&nbsp;— known as [[mogas]] or autogas among aviators&nbsp;— that does not contain ethanol may be used in [[type certificate|certified]] aircraft that have a [[Supplemental Type Certificate]] for automotive gasoline as well as in [[experimental aircraft]] and [[ultralight aviation|ultralight aircraft]]. Some oxygenates other than ethanol are approved. 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]].{{Citation needed|date=July 2013}}

Some aircraft engines were originally certified using a 91/96 avgas and have STCs 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]] does not directly correspond to the 91/96 avgas used to certify engines, as motor vehicle pumps usually 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.{{Citation needed|date=July 2013}}

Automotive gasoline is not a fully viable replacement for avgas in many aircraft, because many high-performance and/or turbocharged airplane engines require 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
|accessdate=2008-12-31
|last=Berry|first = Mike}}</ref>
<ref name="Berry2">{{cite web
|url= http://www.eaa.org/autofuel/autogas/articles/1Autogas%20vs%20Avgas%20Part%202.pdf
|title=Autogas Part 2
|accessdate=2008-12-31
|last=Berry|first=Mike|year=n.d.}}</ref>

Many [[general aviation]] [[aircraft engine]]s were designed to run on 80/87 octane,{{Citation needed|date=April 2008}} roughly the standard for North American automobiles today. Direct conversions to run on automotive fuel are fairly common and applied via the [[supplemental type certificate]] (STC) process. 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.{{Citation needed|date=July 2013}}

Fortunately, significant history of engines converted to mogas has shown that very few engine problems are caused by automotive gasoline{{Citation needed|date=December 2011}}. 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, 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.{{Citation needed|date=July 2013}}

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 for vapor lock from developing.{{Citation needed|date=July 2013}}

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===
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" />
{{See also|Common ethanol fuel mixtures}}

===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|accessdate= 2009-11-30
|publisher=Shell Aviation
|date=July 2008
|archiveurl=http://web.archive.org/web/20080714154427/http://www.shell.com/home/content/aviation-en/productservice/aviationfuels/detail/avgasgradesspecs_10081006.html
|archivedate=2008-07-14}}</ref>
and most are specified by ASTM D910 or other standards.<ref name=ASTM_D910>{{cite web|title=ASTM D910|url=http://www.astm.org/Standards/D910.htm|publisher=ASTM International|accessdate=25 June 2013|location=West Conshohocken, PA, USA}}</ref>
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
|accessdate=10 May 2012}}</ref>

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

|-
|blue
|[[1,4-dialkylaminoanthraquinone]]
|-
|yellow
|[[p-diethylaminoazobenzene]] or 1,3-benzenediol 2,4-bis [(alkylphenyl)azo-]
|-
|red
|alkyl derivatives of [[azobenzene-4-azo-2-naphthol]]
|-
|orange
|[[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
|author=editorial
|date=August 2008
|accessdate=2008-08-28}}</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=2006-08-09
|accessdate=2008-08-28
|archiveurl= http://web.archive.org/web/20080802040502/http://www.aopa.org/whatsnew/regulatory/regunlead.html
|archivedate= 2 August 2008 <!--DASHBot-->|deadurl= no}}</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=2008-08-28
|accessdate=2008-08-28}}
</ref><ref name=AOPA10ll>
{{cite web
|url=http://www.aopa.org/aircraft/articles/2008/080319avgas.html
|title=AOPA working on future avgas
|author= By AOPA ePublishing staff
|work=AOPA onlin
|publisher=Aircraft Owners and Pilots Association
|date=2006-03-19
|accessdate=2008-08-28}}</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
|accessdate= 2008-02-18
|last= AvWeb Staff|year=2008|month=February
|archiveurl= http://web.archive.org/web/20080226084557/http://www.avweb.com/eletter/archives/avflash/1054-full.html
|archivedate= 26 February 2008 <!--DASHBot-->|deadurl= no}}</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 licenced 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
|accessdate= 2008-02-18|last= Bertorelli |first= Paul |year=2008|month=February
|archiveurl= http://web.archive.org/web/20080228035038/http://www.avweb.com/podcast/podcast/197170-1.html
|archivedate= 28 February 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
|accessdate= 12 May 2010|last= Paul|first= Bertorelli |date=May 2010
|archiveurl= http://web.archive.org/web/20100515145705/http://www.avweb.com/avwebflash/news/Continental_DieselEngineProject_202535-1.html
|archivedate= 15 May 2010 <!--DASHBot-->|deadurl= no}}</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?
|accessdate= 13 May 2010|last= Paul|first= Bertorelli |date=12 May 2010
|archiveurl= http://web.archive.org/web/20100520023102/http://www.avweb.com/blogs/insider/AVWebInsider_DieselTCM_202542-1.html
|archivedate= 20 May 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 phase 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
|accessdate= 2008-11-07|last= Niles|first= Russ |date=November 2008}}</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
|accessdate= 21 May 2012
|last= Bertorelli|first= Paul|date=2012-05-20|work= AVweb}}</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
}}</ref> In July 2014, nine companies and consortiums submitted proposals the ''Piston Aviation Fuels Initiative'' (PAMI) to asses 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|magazine=AOPA pilot|date=September 2014|title=FAA to Evaluate nine unleaded fuels|author=Dave Hirschman|page=28}}</ref>

==New unleaded fuel grades==

===93UL===
The firm Airworthy AutoGas tested an ethanol-free premium auto gas on a Lycoming O-360A4M in 2013. The fuel is certified under Lycoming 1070S and ASTM D4814.<ref>{{cite journal|magazine=General Aviation News|date=19 July 2013|page=5|title=Piper Flies on Auto Gas}}</ref>

===94UL===
Unleaded 94-octane fuel (''94UL'') 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 a [[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 is 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
|accessdate= 2009-04-13|last= Bertorelli|first= Paul |date=March 2009
|archiveurl= http://web.archive.org/web/20090406013119/http://www.avweb.com/avwebbiz/news/Continental_94_UL_Replacement_100LL_200048-1.html
|archivedate= 6 April 2009 <!--DASHBot-->|deadurl= no}}</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 |accessdate= 12 May 2010|last= Bertorelli|first= Paul |date=May 2010
|archiveurl= http://web.archive.org/web/20100515125025/http://www.avweb.com/avwebflash/news/TCM_94UL_Replacing_100LL_AlternativeFuels_202536-1.html
|archivedate= 15 May 2010 <!--DASHBot-->|deadurl= no}}</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
|accessdate= 14 June 2010|last= Bertorelli|first= Paul |date= 2010-06-11}}</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
|accessdate= 14 June 2010|last= Pew|first= Glenn |date=June 2010}}</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
|accessdate= 14 June 2010|last= Niles|first= Russ |date=June 2010}}</ref><ref name="100OC">{{cite web
|url= http://www.100octaneformyplane.com/
|title= 100 Octane Unleaded Aviation Fuel - Demand No Less!
|accessdate= 11 September 2010|last= Lee|first= B. |year=2010
|archiveurl= http://web.archive.org/web/20100830222404/http://www.100octaneformyplane.com/
|archivedate= 30 August 2010 <!--DASHBot-->|deadurl= no}}</ref>

===100SF Swift Fuel===
[[Image:Cessna150M-SwiftFuel.jpg|right|thumb|[[Purdue University]] [[Cessna 150M]] Swift Fuel demonstrator]]
{{Redirect3|Swift Fuel}}
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.

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=2006-06-21
|accessdate=2008-08-28
|archiveurl= http://web.archive.org/web/20080810220613/http://www.carrollcountycomet.com/news/2006/0621/front_page/002.html
|archivedate= 10 August 2008 <!--DASHBot-->|deadurl= no}}</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.{{Ref patent
 |country= US
 |number=2008168706
 |status=application
 |title= Renewable Engine Fuel
 |pubdate= 2008-07-17
 |fdate= 2007-07-27
 |invent1= RUSEK, Mary-Louise, R
 |invent2= ZIULKOWSKI, Jonathon, D.
 |assign1= SWIFT ENTERPRISES, LTD.
}}
{{Ref patent
|country=WO
|number=2008013922A1
|status=application
|title=Renewable Engine Fuel
|pubdate=2008-01-31
|fdate=2007-07-27
|pridate=60/833,589 27.07.2006 US
|invent1= RUSEK, Mary-Louise, R
|invent2= ZIULKOWSKI, Jonathon, D.
|assign1=SWIFT ENTPR LTD [US]
|class=C10L1/182; C10L1/185; C10L1/10
}}
</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=2007-11-07
|accessdate=2008-09-18}}
</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=2008-06-13
 |accessdate=2008-06-18}} {{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=2008-08-26
|accessdate=2008-08-28
|archiveurl= http://web.archive.org/web/20080904122727/http://news.medill.northwestern.edu/chicago/news.aspx?id=97989
|archivedate= 4 September 2008 <!--DASHBot-->|deadurl= no}}</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=2008-06-05
|accessdate=2008-06-18}}</ref><ref name=CarrollCountyCometJuly2008>
{{cite news
|url=http://www.carrollcountycomet.com/news/2008/0730/local_news/054.html
|title=Demonstration fuel facility project accelerated
|first=Debbie
|last=Lowe
|work=Carroll County Comet
|location=Flora, Indiana, USA
|date=2008-07-30
|accessdate=2008-08-28}}</ref><ref name=CarrolCountyCometJuly92008>{{cite news
|url=http://www.carrollcountycomet.com/news/2008/0709/front_page/006.html
|title=Annual EDC request approved by Delphi
|first=Debbie
|last=Lowe
|work=Carroll County Comet
|location=Flora, Indiana, USA
|date=2008-07-09
|accessdate=2008-09-18}}
</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=http://www.pbs.org/cringely/pulpit/2008/pulpit_20080606_005036.html
|publisher= PBS
|date=2008-06-06
}}</ref> and 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
|publisher= AOPA
|date=2009-09-03
}}</ref>
Swift Enterprises' claims that 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
|accessdate= 2009-03-05|last= Bertorelli |first= Paul |date=March 2009
|archiveurl= http://web.archive.org/web/20090310002346/http://www.avweb.com/avwebbiz/news/FAAEvaluates100LLAlternative_199892-1.html
|archivedate= 10 March 2009 <!--DASHBot-->|deadurl= no}}</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?
|accessdate= 2009-03-05|last= Bertorelli |first= Paul |date=March 2009
|archiveurl= http://web.archive.org/web/20090312065452/http://www.avweb.com/blogs/insider/AvWebInsider_SwifFuelRealities_199927-1.html
|archivedate= 12 March 2009 <!--DASHBot-->|deadurl= no}}</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
|accessdate= 2010-02-08|last= Bertorelli|first= Paul |year=2010|month=February
|archiveurl= http://web.archive.org/web/20100213042707/http://www.avweb.com/avwebflash/exclusivevids/ExclusiveVideo_G100UL_FuelFlightTest_201983-1.html
|archivedate= 13 February 2010 <!--DASHBot-->|deadurl= no}}</ref><ref name="AvWeb02May10">{{cite web
|url= http://www.avweb.com/blogs/insider/AvWebInsider_GulfDisaster_202481-1.html
|title= Oil Slicks and Avgas
|accessdate= 3 May 2010|last= Bertorelli|first= Paul |date=May 2010
|archiveurl= http://web.archive.org/web/20100507004156/http://www.avweb.com/blogs/insider/AvWebInsider_GulfDisaster_202481-1.html
|archivedate= 7 May 2010 <!--DASHBot-->|deadurl= no}}</ref><ref name="ABS16Jun10">{{cite web
|url= http://www.bonanza.org/News/?id=583
|title= ABS Developing Fuels Strategy|accessdate= 19 June 2010|last= The American Bonanza Society |date=June 2010
|archiveurl= http://web.archive.org/web/20100625080954/http://www.bonanza.org/News/?id=583
|archivedate= 25 June 2010 <!--DASHBot-->|deadurl= no}}</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
|accessdate= 5 July 2010|last= Bertorelli |first= Paul |date=July 2010
|archiveurl= http://web.archive.org/web/20100707084038/http://www.avweb.com/avwebflash/news/SwiftFuelTiltsTowardNa
|archivedate= 7 July 2010 <!--DASHBot-->|deadurl= no}}</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 meets 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 savings of 8% per unit of volume, though it weighs 1 pound per gallon (120 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=2009-03-04
|last= Bertorelli |first= Paul }}</ref><ref name=FAAtest2008>{{cite web
|url=http://www.tc.faa.gov/its/worldpac/techrpt/ar0853.pdf
|format=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}}</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=23 April 2009}} 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=31 March 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}}</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
|accessdate= 2009-03-05|last= Grady |first= Mary |date=December 2009}}</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
|accessdate= 2009-12-17|last=Purdue Research Park |date=December 2009}}</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
|accessdate= 23 August 2010|last= Niles|first= Russ |date=August 2010
|publisher=Aviation Publishing Group|work=Avweb}}</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
|accessdate= 28 October 2010|last= Grady|first= Mary |date=October 2010
|publisher=Aviation Publishing Group|work=Avweb
|archiveurl= http://web.archive.org/web/20101101121151/http://www.avweb.com/avwebflash/news/SwiftFuelExpandsTesting_203523-1.html
|archivedate= 1 November 2010 <!--DASHBot-->|deadurl= no}}</ref> and approved under ASTM specification D7719 for high octane grade UL 102, 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= 25 May 2011
|work=General Aviation News
}}</ref>

In 2012, Swift Fuels LLC was formed to bring in bioenergy experience, scale up production and bring the fuel to market. By November 2013, the company had built and received approval to produce fuel in its pilot plant.<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
}}</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= 2008-07-17
 |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>

===G100UL===
In February 2010, [[General Aviation Modifications Inc.]] announced that they were in the process of developing a 100LL replacement to be called G100UL ("unleaded"). This fuel is made by blending existing refinery products and produces 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. The production economics of this new fuel have not been confirmed but it is anticipated that it will cost at least as much as 100LL.<ref name="Avweb07Feb10B" /><ref name="Avweb07Feb10A">{{cite web
|url= http://www.avweb.com/avwebflash/news/AVwebFliesNewG100ULFuel_201982-1.html
|title= AVweb Flies New G100UL Fuel
|accessdate= 2010-02-08|last= Bertorelli|first= Paul |year=2010|month=February}}</ref>

In demonstrations held in July 2010, G100UL performed better than 100LL that just meets the minimum specification and equal to 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
|accessdate= 8 July 2010
|last= Bertorelli|first= Paul |date=July 2010}}</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=3 December 2013 |accessdate=3 December 2013}}</ref> The fuel is alkylate-based fuel with an additive package of aromatics. No information has yet been published in its performance, producibility or price. Industry analysts have indicated that it will likely cost as much 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=11 December 2013 |accessdate=12 December 2013}}</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. 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
|accessdate= 2008-10-20
|last= Pew|first= Glenn |date=October 2008}}</ref>
<ref name="MarketWatch_WHO">{{cite news
|publisher=MarketWatch.com
|url=http://www.who.int/ceh/publications/leadguidance.pdf
|title= New EPA lead standard significantly improved to protect kids' health
|accessdate= 2008-10-20
|last= Balbus|first= John |date=October 2008}}</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 16 November 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 17 March 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: 16 November 2007 (Volume 72, Number 221)
|accessdate= 2008-02-24
|last= Environmental Protection Agency |date=November 2007}}</ref>

Under a federal court order to set a new standard by 15 October 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 micrograms per cubic meter. 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= http://www.cbc.ca/health/story/2008/10/16/lead-air.html
|title= U.S. tightens health standard for airborne lead
|accessdate= 2008-10-17
|last= [[Canadian Broadcasting Corporation]] |date=October 2008|work=CBC News}}</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".

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
|accessdate= 2008-10-20|last= Hirschman|first= Dave |date=October 2008
|archiveurl= http://web.archive.org/web/20081027085218/http://www.aopa.org/advocacy/articles/2008/081017epa.html
|archivedate= 27 October 2008 <!--DASHBot-->|deadurl= no}}</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 USA 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
|accessdate= 2008-12-08
|last= Pew|first= Glenn|date= 2008-12-05}}</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
|accessdate= 8 April 2010|last= Grady|first= Mary |date=2007-04-10}}</ref><ref name="AvWeb20100410">{{cite web
|url= http://www.avweb.com/avwebflash/news/EPAAdvances100LLRulemakingProcess_202434-1.html
|title= EPA Advances 100LL Rulemaking Process
|accessdate= 22 April 2010|last= Grady|first= Mary |date=2010-04-10}}</ref>

Despite assertions in the media that leaded avgas will be eliminated in the USA 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
|accessdate= 5 July 2010|last= Bertorelli |first= Paul |date=2010-07-04
|archiveurl= http://web.archive.org/web/20100710080511/http://www.avweb.com/blogs/insider/AVwebInsider_FuelFight_202818-1.html
|archivedate= 10 July 2010 <!--DASHBot-->|deadurl= no}}</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|accessdate= 28 July 2010|last= Bertorelli |first= Paul |date=2010-07-28}}</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
|accessdate= 28 July 2010
|last= Bertorelli |first= Paul |date=2010-07-28}}</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
|accessdate= 29 July 2010
|last= Bertorelli |first= Paul |date=2010-07-28}}</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
|accessdate = 29 July 2010
|last= Pew |first= Glenn |date=2010-07-28}}</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
|url= http://www.avweb.com/news/snf/SunNFun2011_TownMeetingIssues_AvgasPilotDecline_204404-1.html
|title="Town Meeting" Issues: Avgas, Pilot Decline
|accessdate= 3 April 2011|last= Grady|first= Mary |date=April 2011|work= AvWeb}}</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>[http://www.smgov.net/uploadedFiles/Departments/Airport/CommissionMeetings/EPA%20Lead%20Modeling%20Study%20Presentation.pdf Final Results from EPA's Lead Modeling Study at the Santa Monica Airport, by Arnold Den, Senior Science Advisor, February 22, 2010]</ref> 15 of 17 airports monitored during a year-long study in the USA 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|url=http://www.aopa.org/News-and-Video/All-News/2013/June/20/ga-community-works-to-replace-100ll.aspx|publisher=Aircraft Owners and Pilots Association|accessdate=23 June 2013|date=2013-06-20|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."}}</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==
*[[Aviation fuel]]
*[[List of CO2 emitted per million Btu of energy from various fuels|Relative CO<sub>2</sub> emission from various fuels]]
*[http://www.aviation-fuel.com/pdfs/avgas100llspecsastmd910_2011.pdf#3 ASTM D910]

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

<!--==External links==-->
[[Category:Air Pollution]]
[[Category:Avgas conservation|*]]