Editing Gasoline (section)

===Antiknock additives===

====Tetraethyl lead====
{{main|Tetraethyl lead}}
<!--This section is linked from [[Lead]]-->

Gasoline, when used in high-[[Compression (physical)|compression]] internal combustion engines, tends to auto-ignite or "detonate" causing damaging [[engine knocking]] (also called "pinging" or "pinking"). To address this problem, [[Tetraethyllead|tetraethyl lead]] (TEL) was widely adopted as an additive for gasoline in the 1920s. With a growing awareness of the seriousness of the extent of environmental and health damage caused by lead compounds, however, and the incompatibility of lead with [[catalytic converter]]s, governments began to mandate reductions in gasoline lead.

In the U.S., the [[Environmental Protection Agency]] issued regulations to reduce the lead content of leaded gasoline over a series of annual phases, scheduled to begin in 1973 but delayed by court appeals until 1976. By 1995, leaded fuel accounted for only 0.6 percent of total gasoline sales and under {{convert|2000|ST|t|abbr=off|sp=us|disp=output only}} ({{convert|{{convert|2000|ST|t|disp=output number only}}|t|ST LT|sp=us|disp=output only}}) of lead per year. From 1 January 1996, the [[Clean Air Act (United States)|U.S. Clean Air Act]] banned the sale of leaded fuel for use in on-road vehicles in the U.S. The use of TEL also necessitated other additives, such as [[dibromoethane]].

European countries began replacing lead-containing additives by the end of the 1980s, and by the end of the 1990s, leaded gasoline was banned within the entire European Union with an exception for [[Avgas#100LL (blue)|Avgas 100LL]] for [[general aviation]].<ref name="q566">{{cite web | last=Calderwood | first=Dave | title=Europe moves to ban lead in avgas | website=FLYER | date=8 March 2022 | url=https://flyer.co.uk/europe-moves-to-ban-lead-in-avgas/ | access-date=28 July 2024}}</ref> The UAE started to switch to unleaded in the early 2000s.<ref>{{Cite web |title=UAE switches to unleaded fuel |date=January 2003 |url=https://gulfnews.com/uae/uae-switches-to-unleaded-fuel-1.343442 |url-status=live |archive-url=https://web.archive.org/web/20200412131951/https://gulfnews.com/uae/uae-switches-to-unleaded-fuel-1.343442 |archive-date=12 April 2020 |access-date=12 April 2020}}</ref>

Reduction in the average lead content of human blood may be a major cause for falling violent crime rates around the world<ref name="WashingtonPostCrime2">{{cite news |last=Matthews |first= Dylan |date=22 April 2013 |title=Lead abatement, alcohol taxes and 10 other ways to reduce the crime rate without annoying the NRA |newspaper=Washington Post |url=https://www.washingtonpost.com/blogs/wonkblog/wp/2013/04/22/lead-abatement-alcohol-taxes-and-10-other-ways-to-reduce-the-crime-rate-without-annoying-the-nra/ |url-status=live |access-date=23 May 2013 |archive-url=https://web.archive.org/web/20130512052321/http://www.washingtonpost.com/blogs/wonkblog/wp/2013/04/22/lead-abatement-alcohol-taxes-and-10-other-ways-to-reduce-the-crime-rate-without-annoying-the-nra/ |archive-date=12 May 2013 |df=dmy-all}}</ref> including South Africa.<ref name="BusinessDayCrime2">{{cite web |last=Marrs |first= Dave |date=22 January 2013 |title=Ban on lead may yet give us respite from crime |url=http://www.bdlive.co.za/opinion/columnists/2013/01/22/ban-on-lead-may-yet-give-us-respite-from-crime |url-status=dead |archive-url=https://web.archive.org/web/20130406072130/http://www.bdlive.co.za/opinion/columnists/2013/01/22/ban-on-lead-may-yet-give-us-respite-from-crime |archive-date=6 April 2013 |access-date=23 May 2013 |publisher=Business Day |df=dmy-all}}</ref> A study found a correlation between leaded gasoline usage and violent crime (see [[Lead–crime hypothesis]]).<ref name="Reyes2">{{Cite web |last=Reyes |first=J. W. |date=2007 |url=https://www.nber.org/system/files/working_papers/w13097/w13097.pdf |title=The Impact of Childhood Lead Exposure on Crime |work=National Bureau of Economic Research. "a" ref citing Pirkle, Brody, et al. (1994) |access-date=26 May 2024 |archive-date=17 January 2024 |archive-url=https://web.archive.org/web/20240117041241/https://www.nber.org/system/files/working_papers/w13097/w13097.pdf |url-status=live }}</ref><ref>{{cite news |date=28 October 2007 |title=Ban on leaded petrol 'has cut crime rates around the world' |url=https://www.independent.co.uk/environment/green-living/ban-on-leaded-petrol-has-cut-crime-rates-around-the-world-398151.html |url-status=live |archive-url=https://web.archive.org/web/20170829032830/https://www.independent.co.uk/environment/green-living/ban-on-leaded-petrol-has-cut-crime-rates-around-the-world-398151.html |archive-date=29 August 2017 |df=dmy-all}}</ref> Other studies found no correlation.

In August 2021, the [[United Nations Environment Programme|UN Environment Programme]] announced that leaded gasoline had been eradicated worldwide, with [[Algeria]] being the last country to deplete its reserves. [[Secretary-General of the United Nations|UN Secretary-General]] [[António Guterres]] called the eradication of leaded petrol an "international success story". He also added: "Ending the use of leaded petrol will prevent more than one million premature deaths each year from heart disease, strokes and cancer, and it will protect children whose IQs are damaged by exposure to lead". [[Greenpeace]] called the announcement "the end of one toxic era".<ref>{{cite web |date=31 August 2021 |title=Highly polluting leaded petrol now eradicated from the world, says UN |url=https://www.bbc.com/news/world-58388810 |url-status=live |archive-url=https://web.archive.org/web/20220125025414/https://www.bbc.com/news/world-58388810 |archive-date=25 January 2022 |access-date=16 September 2021 |work=BBC News}}</ref> However, leaded gasoline continues to be used in aeronautic, auto racing, and off-road applications.<ref>{{cite web |last1=Miranda |first1=Leticia |last2=Farivar |first2=Cyrus |date=12 April 2021 |title=Leaded gas was phased out 25 years ago. Why are these planes still using toxic fuel? |url=https://www.nbcnews.com/business/business-news/leaded-gas-was-phased-out-25-years-ago-why-are-n1264970 |url-status=live |archive-url=https://web.archive.org/web/20210915233641/https://www.nbcnews.com/business/business-news/leaded-gas-was-phased-out-25-years-ago-why-are-n1264970 |archive-date=15 September 2021 |access-date=16 September 2021 |work=NBC News}}</ref> The use of leaded additives is still permitted worldwide for the formulation of some grades of [[aviation gasoline]] such as [[100LL]], because the required octane rating is difficult to reach without the use of leaded additives.

Different additives have replaced lead compounds. The most popular additives include [[aromatic hydrocarbon]]s, [[ether]]s ([[MTBE]] and [[ETBE]]), and [[alcohols]], most commonly [[ethanol]].

====<span class="anchor" id="Lead Replacement Petrol"></span> Lead replacement petrol====
Lead replacement petrol (LRP) was developed for vehicles designed to run on leaded fuels and incompatible with unleaded fuels. Rather than tetraethyllead, it contains other metals such as [[potassium]] compounds or [[methylcyclopentadienyl manganese tricarbonyl]] (MMT); these are purported to buffer soft exhaust valves and seats so that they do not suffer recession due to the use of unleaded fuel.

LRP was marketed during and after the phaseout of leaded motor fuels in the United Kingdom, [[Australia]], [[South Africa]], and some other countries.{{vague|date=August 2016}} Consumer confusion led to a widespread mistaken preference for LRP rather than unleaded,<ref>{{cite news |last=Seggie |first=Eleanor |date=5 August 2011 |title=More than 20% of SA cars still using lead-replacement petrol but only 1% need it |work=[[Engineering News (Creamer Media)|Engineering News]] |location=South Africa |url=http://www.engineeringnews.co.za/article/cleaner-fuels-for-sa-2011-08-05 |url-status=dead |access-date=30 March 2017 |archive-url=https://web.archive.org/web/20161013195145/http://www.engineeringnews.co.za/article/cleaner-fuels-for-sa-2011-08-05 |archive-date=13 October 2016 |df=dmy-all}}</ref> and LRP was phased out 8 to 10 years after the introduction of unleaded.<ref>{{cite news |last1=Clark |first1=Andrew |date=14 August 2002 |title=Petrol for older cars about to disappear |work=[[The Guardian]] |location=London |url=https://www.theguardian.com/uk/2002/aug/15/oil.business |url-status=live |access-date=30 March 2017 |archive-url=https://web.archive.org/web/20161229112618/https://www.theguardian.com/uk/2002/aug/15/oil.business |archive-date=29 December 2016 |df=dmy-all}}</ref>

Leaded gasoline was withdrawn from sale in Britain after 31 December 1999, seven years after [[European Economic Community|EEC]] regulations signaled the end of production for cars using leaded gasoline in member states. At this stage, a large percentage of cars from the 1980s and early 1990s which ran on leaded gasoline were still in use, along with cars that could run on unleaded fuel. However, the declining number of such cars on British roads saw many gasoline stations withdrawing LRP from sale by 2003.<ref>{{Cite news |date=15 August 2002 |title=AA warns over lead replacement fuel |work=[[The Daily Telegraph]] |location=London |url=https://www.telegraph.co.uk/motoring/news/2717637/AA-warns-over-lead-replacement-fuel.html |url-status=live |access-date=30 March 2017 |archive-url=https://web.archive.org/web/20170421115246/http://www.telegraph.co.uk/motoring/news/2717637/AA-warns-over-lead-replacement-fuel.html |archive-date=21 April 2017 |df=dmy-all}}</ref>

====MMT====
[[Methylcyclopentadienyl manganese tricarbonyl]] (MMT) is used in Canada and the U.S. to boost octane rating.<ref>{{cite web |last1=Hollrah |first1=Don P. |last2=Burns |first2=Allen M. |date=11 March 1991 |title=MMT Increases Octane While Reducing Emissions |url=http://www.ogj.com/articles/print/volume-89/issue-10/in-this-issue/refining/mmt-increases-octane-while-reducing-emissions.html |url-status=live |archive-url=https://web.archive.org/web/20161117072536/http://www.ogj.com/articles/print/volume-89/issue-10/in-this-issue/refining/mmt-increases-octane-while-reducing-emissions.html |archive-date=17 November 2016 |website=www.ogj.com |df=dmy-all}}</ref> Its use in the U.S. has been restricted by regulations, although it is currently allowed.<ref>{{cite web |date=5 October 2015 |title=EPA Comments on the Gasoline Additive MMT |url=https://www.epa.gov/gasoline-standards/epa-comments-gasoline-additive-mmt |url-status=live |archive-url=https://web.archive.org/web/20161117070650/https://www.epa.gov/gasoline-standards/epa-comments-gasoline-additive-mmt |archive-date=17 November 2016 |website=www.epa.gov |language=en |df=dmy-all}}</ref> Its use in the European Union is restricted by Article 8a of the Fuel Quality Directive<ref>{{cite web |title=Directive 2009/30/EC of the European Parliament and of the Council of 23 April 2009 |url=http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2009:140:0088:0113:EN:PDF |url-status=live |archive-url=https://web.archive.org/web/20160922172330/http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2009:140:0088:0113:EN:PDF |archive-date=22 September 2016 |access-date=July 31, 2020}}</ref> following its testing under the Protocol for the evaluation of effects of metallic fuel-additives on the emissions performance of vehicles.<ref>{{cite web |title=Protocol for the Evaluation of Effects of Metallic Fuel-Additives on the Emissions Performance of Vehicles |url=https://ec.europa.eu/clima/sites/clima/files/transport/fuel/docs/fuel_metallic_additive_protocol_en.pdf |url-status=live |archive-url=https://web.archive.org/web/20210301173052/https://ec.europa.eu/clima/sites/clima/files/transport/fuel/docs/fuel_metallic_additive_protocol_en.pdf |archive-date=1 March 2021 |access-date=July 31, 2020}}</ref>