View source for Diesel fuel

{{short description|Liquid fuel used in diesel engines}}
{{Redirect|Gas oil|gas oil as other classes of fuel oil|Fuel oil}}
{{Redirect-distinguish-text|Diesel oil|[[lubricating oil]] for diesel engines}}
[[File:Red diesel tank.jpg|thumb|upright=1.3|A tank of diesel fuel on a truck]]

'''Diesel fuel''', also called '''diesel oil''', '''heavy oil''' (historically) or simply '''diesel''', is any [[liquid fuel]] specifically designed for use in a [[diesel engine]], a type of [[internal combustion engine]] in which fuel ignition takes place without a spark as a result of compression of the inlet air and then injection of fuel. Therefore, diesel fuel needs good compression ignition characteristics.

The most common type of diesel fuel is a specific [[fractional distillation|fractional distillate]] of [[petroleum]] [[fuel oil]], but alternatives that are not derived from petroleum, such as [[biodiesel]], [[biomass to liquid]] (BTL) or [[gas to liquid]] (GTL) diesel are increasingly being developed and adopted. To distinguish these types, petroleum-derived diesel is sometimes called '''petrodiesel''' in some academic circles.<ref>{{Cite journal | doi=10.1021/ef0502711|title = Exhaust Emissions of Biodiesel, Petrodiesel, Neat Methyl Esters, and Alkanes in a New Technology Engine†| journal=Energy & Fuels| volume=20| pages=403–408|year = 2006|last1 = Knothe|first1 = Gerhard| last2=Sharp| first2=Christopher A.| last3=Ryan| first3=Thomas W.| s2cid=53386870}}</ref> Diesel is a high-volume product of oil refineries.<ref>{{Cite book |last=Gary |first=James H. |title=Petroleum refining: technology and economics |last2=Handwerk |first2=Glenn E. |date=2001 |publisher=Dekker |isbn=978-0-8247-0482-7 |edition=4. |location=New York Basel |page=1}}</ref>

In many countries, diesel fuel is standardized. For example, in the European Union, the standard for diesel fuel is [[EN 590]]. [[Ultra-low-sulfur diesel]] (ULSD) is a diesel fuel with substantially lowered [[sulfur]] contents. As of 2016, almost all of the petroleum-based diesel fuel available in the United Kingdom, mainland Europe, and North America is of a ULSD type. Before diesel fuel had been standardized, the majority of diesel engines typically ran on cheap [[fuel oil]]s. These fuel oils are still used in watercraft diesel engines. Despite being specifically designed for diesel engines, diesel fuel can also be used as fuel for several non-diesel engines, for example the [[Akroyd engine]], the [[Stirling engine]], or boilers for [[steam engine]]s. Diesel is often used in [[heavy truck]]s. However, [[diesel exhaust]], especially from older engines, can cause health damage.<ref>{{Cite web |last=US EPA |first=OAR |date=2015-07-24 |title=Learn About Impacts of Diesel Exhaust and the Diesel Emissions Reduction Act (DERA) |url=https://www.epa.gov/dera/learn-about-impacts-diesel-exhaust-and-diesel-emissions-reduction-act-dera |access-date=2023-04-29 |website=www.epa.gov |language=en}}</ref><ref>{{Cite web |date=2023-04-29 |title=California approves rule phasing out big diesel trucks |url=https://abc7.com/big-rig-bus-diesel-ban/13195644/ |access-date=2023-04-29 |website=ABC7 Los Angeles |language=en |archive-date=2023-04-29 |archive-url=https://web.archive.org/web/20230429181156/https://abc7.com/big-rig-bus-diesel-ban/13195644/ |url-status=dead}}</ref>

== Names ==
Diesel fuel has many colloquial names; most commonly, it is simply referred to as ''diesel''. In the United Kingdom, diesel fuel for road use is commonly called ''diesel'' or sometimes ''white diesel'' if required to differentiate it from a reduced-tax [[non-road diesel engine|agricultural-only]] product containing an [[Fuel dye#United Kingdom|identifying coloured dye]] known as ''red diesel''. The official term for white diesel is ''DERV'', standing for ''diesel-engine road vehicle''.<ref>{{cite web |date=8 November 2022 |title=DERV FAQ |url=https://www.nationwidefuels.co.uk/faq/white-diesel-faq/ |publisher=Nationwide Fuels and Lubricants Ltd. |page=5}}</ref> In [[Australia]], diesel fuel is also known as '''distillate'''<ref>The Macquarie Dictionary 3rd ed, The Macquarie Library 1997</ref> (not to be confused with [[distillate (motor fuel)|"distillate"]] in an older sense referring to a different motor fuel), and in [[Indonesia]] (as well in [[Israel]]), it is known as '''Solar''', a trademarked name from the country's national petroleum company [[Pertamina]]. The term '''gas oil''' (French: ''gazole'') is sometimes also used to refer to diesel fuel.

== History ==
=== Origins ===
Diesel fuel originated from experiments conducted by German scientist and inventor [[Rudolf Diesel]] for his [[compression-ignition engine]] which he invented around 1892. Originally, Diesel did not consider using any specific type of fuel. Instead, he claimed that the operating principle of his [[Theory and Construction of a Rational Heat Motor|rational heat motor]] would work with any kind of fuel in any state of matter.<ref>{{patent|DE|67207|Rudolf Diesel: "Arbeitsverfahren und Ausführungsart für Verbrennungskraftmaschinen" pg 4.}}: "Alle Brennmaterialien in allen Aggregatzuständen sind für Durchführung des Verfahrens brauchbar."</ref> The first diesel engine prototype and the first functional Diesel engine were only designed for liquid fuels.<ref>Rudolf Diesel: ''Die Entstehung des Dieselmotors'', Springer, Berlin/Heidelberg 1913, {{ISBN|978-3-642-64940-0}} p. 125</ref>

At first, Diesel tested [[crude oil]] from [[Pechelbronn]], but soon replaced it with [[petrol]] and [[kerosene]], because crude oil proved to be too viscous,<ref>Rudolf Diesel: ''Die Entstehung des Dieselmotors'', Springer, Berlin/Heidelberg 1913, {{ISBN|978-3-642-64940-0}} p. 107</ref> with the main testing fuel for the Diesel engine being kerosene ([[Mineral oil|paraffin]]).<ref>Rudolf Diesel: ''Die Entstehung des Dieselmotors'', Springer, Berlin/Heidelberg 1913, {{ISBN|978-3-642-64940-0}} p. 108</ref> Diesel experimented with types of [[lamp oil]] from various sources, as well as types of petrol and [[ligroin]], which all worked well as Diesel engine fuels. Later, Diesel tested [[coal tar]] [[creosote]],<ref>Rudolf Diesel: ''Die Entstehung des Dieselmotors'', Springer, Berlin/Heidelberg 1913, {{ISBN|978-3-642-64940-0}} p. 110</ref> paraffin oil, crude oil, [[gasoline]] and [[fuel oil]], which eventually worked as well.<ref>Rudolf Diesel: ''Die Entstehung des Dieselmotors'', Springer, Berlin/Heidelberg 1913, {{ISBN|978-3-642-64940-0}} p. 111</ref> In Scotland and France, [[shale oil]] was used as fuel for the first 1898 production Diesel engines because other fuels were too expensive.<ref>Rudolf Diesel: ''Die Entstehung des Dieselmotors'', Springer, Berlin/Heidelberg 1913, {{ISBN|978-3-642-64940-0}} p. 114</ref> In 1900, the French Otto society built a Diesel engine for the use with crude oil, which was exhibited at the [[Exposition Universelle (1900)|1900 Paris Exposition]]<ref name="Diesel_115">Rudolf Diesel: ''Die Entstehung des Dieselmotors'', Springer, Berlin/Heidelberg 1913, {{ISBN|978-3-642-64940-0}} p. 115</ref> and the 1911 World's Fair in Paris.<ref>{{cite book |author=Ayhan Demirbas |title=Biodiesel: A Realistic Fuel Alternative for Diesel Engines |publisher=Springer |location=Berlin |year=2008 |pages=74 |isbn=978-1-84628-994-1 |url= https://books.google.com/books?id=0vBalrSH_OEC&q=Rudolf+Diesel+vegetable&pg=PA74}}</ref> The engine actually ran on [[peanut oil]] instead of crude oil, and no modifications were necessary for peanut oil operation.<ref name="Diesel_115" />

During his first Diesel engine tests, Diesel also used [[illuminating gas]] as fuel, and managed to build functional designs, both with and without pilot injection.<ref>Rudolf Diesel: ''Die Entstehung des Dieselmotors'', Springer, Berlin/Heidelberg 1913, {{ISBN|978-3-642-64940-0}} p. 116</ref> According to Diesel, neither was a coal-dust–producing industry existent, nor was fine, high-quality coal-dust commercially available in the late 1890s. This is the reason why the Diesel engine was never designed or planned as a coal-dust engine.<ref>Rudolf Diesel: ''Die Entstehung des Dieselmotors'', Springer, Berlin/Heidelberg 1913, {{ISBN|978-3-642-64940-0}} p. 126</ref> Only in December 1899, did Diesel test a coal-dust prototype, which used external mixture formation and liquid fuel pilot injection.<ref>Rudolf Diesel: ''Die Entstehung des Dieselmotors'', Springer, Berlin/Heidelberg 1913, {{ISBN|978-3-642-64940-0}} p. 127</ref> This engine proved to be functional, but suffered from piston ring failure after a few minutes due to coal dust deposition.<ref>Friedrich Sass: ''Geschichte des deutschen Verbrennungsmotorenbaues von 1860 bis 1918'', Springer, Berlin/Heidelberg 1962, {{ISBN|978-3-662-11843-6}} p. 499</ref>

=== Since the 20th century ===

Before diesel fuel was standardised, diesel engines typically ran on cheap fuel oils. In the United States, these were distilled from petroleum, whereas in Europe, coal-tar creosote oil was used. Some diesel engines were fuelled with mixtures of fuels, such as petrol, kerosene, rapeseed oil, or lubricating oil which were cheaper because, at the time, they were not being taxed.<ref>Hans Christian Graf von Seherr-Thoß (auth.): Die Technik des MAN Nutzfahrzeugbaus. In: MAN Nutzfahrzeuge AG (ed.): Leistung und Weg: Zur Geschichte des MAN Nutzfahrzeugbaus. Springer, Berlin/Heidelberg 1991. {{ISBN|978-3-642-93490-2}}. p. 436</ref> The introduction of motor-vehicle diesel engines, such as the [[Mercedes-Benz OM 138]], in the 1930s meant that higher-quality fuels with proper ignition characteristics were needed. At first no improvements were made to motor-vehicle diesel fuel quality. After World War II, the first modern high-quality diesel fuels were standardised. These standards were, for instance, the DIN 51601, VTL 9140–001, and NATO F 54 standards.<ref name="Seher-Thoß_437">Hans Christian Graf von Seherr-Thoß (auth.): Die Technik des MAN Nutzfahrzeugbaus. In: MAN Nutzfahrzeuge AG (ed.): Leistung und Weg: Zur Geschichte des MAN Nutzfahrzeugbaus. Springer, Berlin/Heidelberg 1991. {{ISBN|978-3-642-93490-2}}. p. 437</ref> In 1993, the DIN 51601 was rendered obsolete by the new EN 590 standard, which has been used in the European Union ever since. In sea-going watercraft, where diesel propulsion had gained prevalence by the late 1970s due to increasing fuel costs caused by the [[1970s energy crisis]], cheap [[heavy fuel oil]]s are still used instead of conventional motor-vehicle diesel fuel. These heavy fuel oils (often called [[Bunker C]]) can be used in diesel-powered and steam-powered vessels.<ref name="Mau_13">Günter Mau: Handbuch Dieselmotoren im Kraftwerks- und Schiffsbetrieb, Springer-Vieweg, Braunschweig/Wiesbaden 1984, {{ISBN|978-3-528-14889-8}}. p. 13</ref>

== Types ==
Diesel fuel is produced from various sources, the most common being [[petroleum]]. Other sources include [[biomass]], [[animal fat]], [[biogas]], [[natural gas]], and [[coal liquefaction]].

=== Petroleum diesel ===
[[File:essodiesel.jpg|thumb|right|A modern diesel dispenser]]

Petroleum diesel is the most common type of diesel fuel. It is produced by the [[fractional distillation]] of [[crude oil]] between {{cvt|200|and|350|C}} at [[atmospheric pressure]], resulting in a mixture of carbon chains that typically contain between 9 and 25 [[carbon]] [[atom]]s per [[molecule]].<ref>ITRC (Interstate Technology & Regulatory Council). 2014. Petroleum Vapor Intrusion: Fundamentals of Screening, Investigation, and Management. PVI-1. Washington, D.C.: Interstate Technology & Regulatory Council, Petroleum Vapor Intrusion Team. [http://www.itrcweb.org/PetroleumVI-Guidance] {{Webarchive|url=https://web.archive.org/web/20200404221020/https://www.itrcweb.org/PetroleumVI-Guidance/|date=2020-04-04}}</ref>  This fraction is subjected to [[hydrodesulfurization]].

Usually such "straight-run" diesel is insufficient in supply and quality, so other sources of diesel fuels are blended in.  One major source of additional diesel fuel is obtained by cracking heavier fractions, using [[visbreaker|visbreaking]] and coking.  This technology converts less useful fractions but the product contains olefins ([[alkene]]s) which require [[hydrogenation]] to give the saturated hydrocarbons as desired.  Another refinery stream that contributes to diesel fuel is [[hydrocracking]].  Finally, [[kerosene]] is added to modify its viscosity.<ref name="Ullmann2">Werner Dabelstein, Arno Reglitzky, Andrea Schütze and Klaus Reders "Automotive Fuels" in ''Ullmann's Encyclopedia of Industrial Chemistry'' 2007, Wiley-VCH, Weinheim. {{doi|10.1002/14356007.a16_719.pub2}}</ref>

=== Synthetic diesel ===
{{Main|Synthetic fuel}}
Synthetic diesel can be produced from many carbonaceous precursors but natural gas is most important. Raw materials are converted to [[syngas|synthesis gas]] which by the [[Fischer–Tropsch process]] is converted to a synthetic diesel.<ref>{{cite web|title=Synthetic Diesel May Play a Significant Role as Renewable Fuel in Germany |url=http://www.fas.usda.gov/pecad2/highlights/2005/01/btl0104/syntheticdiesel.htm |date=January 25, 2005 |work=[[United States Department of Agriculture|USDA]] Foreign Agricultural Service website |url-status=dead |archive-url=https://web.archive.org/web/20060927153022/http://www.fas.usda.gov/pecad2/highlights/2005/01/btl0104/syntheticdiesel.htm |archive-date=2006-09-27 }}</ref> Synthetic diesel produced in this way generally is mainly paraffins with low sulfur and aromatics content.  This material is blended often into the above mentions petroleum derived diesel.<ref name="Ullmann2"/>

=== Biodiesel ===
{{Main|Biodiesel}}
[[File:Bequer-B100-SOJA-SOYBEAM.jpg|thumb|right|upright|[[Biodiesel]] made from [[soybean oil]]]]

[[Biodiesel]] is obtained from [[vegetable oil]] or animal fats (bio[[lipid]]s) which are mainly [[fatty acid methyl ester]]s (FAME), and [[transesterification|transesterified]] with [[methanol]]. It can be produced from many types of oils, the most common being [[rapeseed]] oil (rapeseed methyl ester, RME) in Europe and [[soybean oil]] (soy methyl ester, SME) in the US. Methanol can also be replaced with ethanol for the transesterification process, which results in the production of ethyl esters. The transesterification processes use catalysts, such as sodium or potassium hydroxide, to convert vegetable oil and methanol into biodiesel and the undesirable byproducts glycerine and water, which will need to be removed from the fuel along with methanol traces. Biodiesel can be used pure (B100) in engines where the manufacturer approves such use, but it is more often used as a mix with diesel, BXX where XX is the biodiesel content in percent.<ref name="Bosch">Bosch Automotive Handbook, 6th edition, pp. 327–328</ref><ref name="acea.be">{{cite web |url=http://www.acea.be/images/uploads/070208_ACEA_FAME_BTL_final.pdf |title=ACEA Position on the use of bio-diesel (FAME) and synthetic bio-fuel in compression-ignition engines |publisher=acea.be |access-date=2010-08-21 |url-status=dead |archive-url=https://web.archive.org/web/20110611201410/http://www.acea.be/images/uploads/070208_ACEA_FAME_BTL_final.pdf |archive-date=2011-06-11 }}</ref>

FAME used as fuel is specified in [[EN 14214|DIN EN 14214]]<ref>{{cite web |url=http://www.worldenergy.net/products/biodiesel/eu_specs.php |title=Biodiesel: EU Specifications |publisher=World Energy |access-date=2010-08-21 |archive-date=2011-07-24 |archive-url=https://web.archive.org/web/20110724132859/http://www.worldenergy.net/products/biodiesel/eu_specs.php |url-status=dead }}</ref> and ASTM D6751 standards.<ref>{{cite web |title=Biodiesel: ASTM International Specifications (B100) |url=http://www.worldenergy.net/products/biodiesel/us_specs.php |publisher=World Energy |url-status=live |archive-url=https://web.archive.org/web/20070917072738/http://www.worldenergy.net/products/biodiesel/us_specs.php|archive-date=17 September 2007 }}</ref>
<!-- off topic or tangential.  This section is about the sources of diesel, period.
Fuel Injection Equipment (FIE) manufacturers have raised several concerns regarding biodiesel, identifying FAME as being the cause of the following problems: corrosion of fuel injection components, low-pressure fuel system blockage, increased dilution and [[polymerization]] of engine sump oil, pump seizures due to high fuel viscosity at low temperature, increased injection pressure, elastomeric seal failures and fuel injector spray blockage.<ref>{{cite web |url=http://journeytoforever.org/biofuel_library/FIEM.pdf |title=Fatty Acid Methyl Ester Fuels as a Replacement or Extender for Diesel Fuels |publisher=FAME Fuel - Joint FIE Manufacturers Statement |date=June 2000 |access-date=14 March 2022}}</ref> Pure biodiesel has an energy content about 5–10% lower than petroleum diesel.<ref>{{Cite news |url=http://www.biodiesel.com/biodiesel/benefits/ |title=Biodiesel Benefits - Why Use Biodiesel? - Pacific Biodiesel |newspaper=Pacific Biodiesel |access-date=2017-02-14 |language=en-US |archive-url=https://web.archive.org/web/20170625021106/http://www.biodiesel.com/biodiesel/benefits/ |archive-date=2017-06-25 |url-status=dead}}</ref> The loss in power when using pure biodiesel is 5–7%.<ref name="acea.be" />

[[Unsaturated fatty acid]]s are the source for the lower oxidation stability. They react with oxygen and form peroxides and result in degradation byproducts, which can cause sludge and lacquer in the fuel system.<ref>{{cite web |url=http://altfuelsgroup.org/site/images/M_images/projects/b100overview.pdf |title=Lubrizol B100 Overview |date=September 2007 |publisher=Lubrizol Corporation |access-date=14 March 2022}}</ref>

As biodiesel contains low levels of sulfur, the emissions of [[sulfur oxide]]s and [[sulfate]]s, major components of [[acid rain]], are low. Use of biodiesel also results in reductions of unburned hydrocarbons, [[carbon monoxide]] (CO), and particulate matter. CO emissions using biodiesel are substantially reduced, on the order of 50% compared to most petrodiesel fuels. The exhaust emissions of particulate matter from biodiesel have been found to be 30% lower than overall particulate matter emissions from petrodiesel. The exhaust emissions of total hydrocarbons (a contributing factor in the localized formation of smog and ozone) are up to 93% lower for biodiesel than diesel fuel.{{Citation needed|date=April 2023}}-->

== Storage and additives==
[[File:Diesel tanks near Hermannin rantatie in Hermanninranta, Sörnäinen, Helsinki, Finland, 2021 July.jpg|thumb|Large diesel fuel tanks in [[Sörnäinen]], [[Helsinki]], [[Finland]]]]
In the US, diesel is recommended to be stored in a yellow container to differentiate it from [[kerosene]], which is typically kept in blue containers, and [[gasoline]] (petrol), which is typically kept in red containers.<ref name=bhm199702>{{cite journal|last=Warner|first=Emory|title=For safety sake, homestead fuel storage must be handled properly|journal=[[Backwoods Home Magazine]]|issue=43|date=February 1997|url=http://www.backwoodshome.com/articles/warner43.html}}</ref> In the UK, diesel is normally stored in a black container to differentiate it from unleaded or leaded petrol, which are stored in green and red containers, respectively.<ref name="hseuk">{{cite web|title=Petroleum – frequently asked questions|url=http://www.hse.gov.uk/fireandexplosion/petroleum-faqs.htm|author=<!--Staff writer(s); no by-line.-->|date=6 December 2013|website=hse.gov.uk|publisher=Health and Safety Executive|url-status=live|archive-url=https://web.archive.org/web/20120105160357/http://www.hse.gov.uk/fireandexplosion/petroleum-faqs.htm|archive-date=5 January 2012|access-date=18 July 2014}}</ref>

[[Ethylene-vinyl acetate]] (EVA) is added to diesel as a "cold flow improver".  50-500 ppm of EVA inhibits crystallization of waxes, which can block fuel filters.  Antifoaming agents ([[silicone]]s), antioxidants ([[hindered phenol]]s), and "metal deactivating agents" (salicylaldimines) are other additives.  Their use is dictated by the particular composition of and storage plans for diesel fuels.  Each is added at the 5-50 ppm level.<ref name="Ullmann2"/>

== Standards ==

The diesel engine is a multifuel engine and can run on a huge variety of fuels. However, development of high-performance, high-speed diesel engines for cars and lorries in the 1930s meant that a proper fuel specifically designed for such engines was needed: diesel fuel. In order to ensure consistent quality, diesel fuel is standardised; the first standards were introduced after World War II.<ref name="Seher-Thoß_437" /> Typically, a standard defines certain properties of the fuel, such as [[cetane number]], [[density]], [[flash point]], [[sulphur]] content, or biodiesel content. Diesel fuel standards include:

'''Diesel fuel'''
* [[EN 590]] (European Union)
* ASTM D975 (United States)
* GOST R 52368 (Russia; equivalent to EN 590)
* NATO F 54 (NATO; equivalent to EN 590)
* DIN 51601 (West Germany; obsolete)

'''Biodiesel fuel'''
* [[EN 14214]] (European Union)
* ASTM D6751 (United States)
* CAN/CGSB-3.524 (Canada)

== Measurements and pricing ==

=== Cetane number ===
{{Main|Cetane number}}
The principal measure of diesel fuel quality is its [[cetane number]]. A cetane number is a measure of the delay of ignition of a diesel fuel.<ref name="ufa1" /> A higher cetane number indicates that the fuel ignites more readily when sprayed into hot compressed air.<ref name="ufa1" /> European (EN 590 standard) road diesel has a minimum cetane number of 51. Fuels with higher cetane numbers, normally "premium" diesel fuels with additional cleaning agents and some synthetic content, are available in some markets.

=== Fuel value and price ===
{{Further|Gasoline and diesel usage and pricing}}

About 86.1% of diesel fuel mass is carbon, and when burned, it offers a net heating value of 43.1 MJ/kg as opposed to 43.2 MJ/kg for gasoline. Due to the higher density, diesel fuel offers a higher volumetric energy density: the density of EN 590 diesel fuel is defined as {{cvt|0.820|to|0.845|kg/L|lb/USgal}} at {{cvt|15|C}}, about 9.0-13.9% more than EN 228 gasoline (petrol)'s {{cvt|0.720|-|0.775|kg/L|lb/USgal}} at 15&nbsp;°C, which should be put into consideration when comparing volumetric fuel prices. The {{CO2}} emissions from diesel are 73.25 g/MJ, just slightly lower than for gasoline at 73.38 g/MJ.<ref>{{cite web|url=http://ies.jrc.ec.europa.eu/uploads/media/TTW_Report_010307.pdf|title=Table 2.1|url-status=dead|archive-url=https://web.archive.org/web/20110720162258/http://ies.jrc.ec.europa.eu/uploads/media/TTW_Report_010307.pdf|archive-date=2011-07-20}}</ref>

Diesel fuel is generally simpler to refine from petroleum than gasoline. Additional refining is required to remove sulfur, which contributes to a sometimes higher cost. In many parts of the United States and throughout the United Kingdom and Australia,<ref>{{cite web|url=http://www.aip.com.au/pricing/facts/Facts_about_Diesel_Prices.htm|title=Facts about Diesel Prices|access-date=2008-07-17|archive-url=https://web.archive.org/web/20080719113021/http://www.aip.com.au/pricing/facts/Facts_about_Diesel_Prices.htm|archive-date=2008-07-19|url-status=dead}}</ref> diesel fuel may be priced higher than petrol per [[gallon]] or [[liter]].<ref>{{cite web|url=http://tonto.eia.doe.gov/oog/info/gdu/gasdiesel.asp|archive-url=https://web.archive.org/web/20010815085245/http://tonto.eia.doe.gov/oog/info/gdu/gasdiesel.asp|url-status=dead|archive-date=2001-08-15|title=Gasoline and Diesel Fuel Update - Energy Information Administration}}</ref><ref>{{cite web | url=https://carplus.co.uk/magazine/petrol-vs-diesel/ | title=Petrol vs. Diesel: Should I Buy a Diesel Car in 2022? &#124; Carplus }}</ref> Reasons for higher-priced diesel include the shutdown of some refineries in the [[Gulf of Mexico]], diversion of mass refining capacity to gasoline production, and a recent transfer to [[ultra-low-sulfur diesel]] (ULSD), which causes infrastructural complications.<ref>{{Cite web |url=http://www.eia.doe.gov/bookshelf/brochures/diesel/dieselprices2006.html |title=A Primer on Diesel Fuel Prices |publisher=Energy Information Administration |access-date=2007-03-27 |archive-url=https://web.archive.org/web/20070317055519/http://www.eia.doe.gov/bookshelf/brochures/diesel/dieselprices2006.html |archive-date=2007-03-17 |url-status=dead }}</ref> In Sweden, a diesel fuel designated as MK-1 (class 1 environmental diesel) is also being sold. This is a ULSD that also has a lower aromatics content, with a limit of 5%.<ref>[http://www.criterioncatalysts.com/static/criterion-gb/downloads/pdf/technical_papers/cri707ertc06.pdf]{{dead link|date=September 2017|bot=InternetArchiveBot|fix-attempted=yes}}</ref> This fuel is slightly more expensive to produce than regular ULSD. In Germany, the fuel tax on diesel fuel is about 28% lower than the petrol fuel tax.

=== Taxation ===
Diesel fuel is similar to [[heating oil]], which is used in [[central heating]]. In Europe, the United States, and Canada, [[tax]]es on diesel fuel are higher than on heating oil due to the [[fuel tax]], and in those areas, heating oil is marked with [[fuel dyes]] and trace chemicals to prevent and detect [[tax fraud]]. "Untaxed" diesel (sometimes called "off-road diesel" or "red diesel" due to its red dye) is available in some countries for use primarily in agricultural applications, such as fuel for tractors, recreational and utility vehicles or other [[non-commercial|noncommercial]] vehicles that do not use [[public road]]s. This fuel may have sulfur levels that exceed the limits for road use in some countries (e.g. US).

This untaxed diesel is dyed red for identification,<ref name="26 CFR 48.4082-1">{{cite web
 |url=http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=5e6923448149c8865561ae47adaf28a7&rgn=div8&view=text&node=26:16.0.1.1.6.5.14.41&idno=26
 |title=Title 26, §&nbsp;48.4082–1 Diesel fuel and kerosene; exemption for dyed fuel.
 |access-date=2006-11-28
 |author=United States Government Printing Office
 |author-link=United States Government Printing Office
 |date=2006-10-25
 |work=Electronic Code of Federal Regulations (e-CFR)
 |quote=Diesel fuel or kerosene satisfies the dyeing requirement of this paragraph (b) only if the diesel fuel or kerosene contains— (1) The dye Solvent Red 164 (and no other dye) at a concentration spectrally equivalent to at least 3.9 pounds of the solid dye standard Solvent Red 26 per thousand barrels of diesel fuel or kerosene; or (2) Any dye of a type and in a concentration that has been approved by the Commissioner.
 |url-status=dead
 |archive-url=https://web.archive.org/web/20070323020523/http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=5e6923448149c8865561ae47adaf28a7&rgn=div8&view=text&node=26%3A16.0.1.1.6.5.14.41&idno=26
 |archive-date=2007-03-23
 }} Cited as 26 CFR 48.4082-1. This regulation implements {{usc|26|4082-1}}.</ref> and using this untaxed diesel fuel for a typically taxed purpose (such as driving use), the user can be fined (e.g. US$10,000 in the US). In the United Kingdom, Belgium and the Netherlands, it is known as [[red diesel]] (or gas oil), and is also used in [[agricultural]] vehicles, home heating tanks, refrigeration units on vans/trucks which contain perishable items such as food and medicine and for marine craft. Diesel fuel, or marked gas oil is dyed green in the Republic of Ireland and Norway. The term "diesel-engined road vehicle" (DERV) is used in the UK as a synonym for unmarked road diesel fuel. In India, taxes on diesel fuel are lower than on petrol, as the majority of the transportation for grain and other essential commodities across the country runs on diesel.

Taxes on [[biodiesel]] in the US vary between states. Some states (Texas, for example) have no tax on biodiesel and a reduced tax on biodiesel blends equivalent to the amount of biodiesel in the blend, so that B20 fuel is taxed 20% less than pure petrodiesel.<ref>{{cite web |url=http://www.eere.energy.gov/afdc/progs/ind_state_laws.php/TX/BIOD |title=Texas Biodiesel Laws and Incentives |publisher=U.S. Department of Energy |access-date=2008-02-29 |url-status=dead |archive-url=https://web.archive.org/web/20080205060806/http://www.eere.energy.gov/afdc/progs/ind_state_laws.php/TX/BIOD |archive-date=2008-02-05 }}</ref> Other states, such as North Carolina, tax biodiesel (in any blended configuration) the same as petrodiesel, although they have introduced new incentives to producers and users of all biofuels.<ref>{{cite web |url=http://www.eere.energy.gov/afdc/progs/ind_state_laws.php/NC/BIOD |title=North Carolina Biodiesel Laws and Incentives |url-status=dead |archive-url=https://web.archive.org/web/20071130001952/http://www.eere.energy.gov/afdc/progs/ind_state_laws.php/NC/BIOD |archive-date=2007-11-30 }}</ref>

== Uses ==

Diesel fuel is mostly used in high-speed diesel engines, especially motor-vehicle (e.g. car, lorry) diesel engines, but not all diesel engines run on diesel fuel. For example, large two-stroke watercraft engines typically use heavy fuel oils instead of diesel fuel,<ref name="Mau_13" /> and certain types of diesel engines, such as MAN [[M-System]] engines, are designed to run on petrol with knock resistances of up to 86&nbsp;RON.<ref>Hans Christian Graf von Seherr-Thoß (auth.): Die Technik des MAN Nutzfahrzeugbaus. In: MAN Nutzfahrzeuge AG (ed.): Leistung und Weg: Zur Geschichte des MAN Nutzfahrzeugbaus. Springer, Berlin/Heidelberg 1991. {{ISBN|978-3-642-93490-2}}. p. 438</ref> On the other hand, [[gas turbine]] and some other types of internal combustion engines, and [[external combustion engine]]s, can also be designed to take diesel fuel.

The [[viscosity]] requirement of diesel fuel is usually specified at 40&nbsp;°C.<ref name="ufa1" /> A disadvantage of diesel fuel in cold climates is that its viscosity increases as the temperature decreases, changing it into a [[gel]] (see [[Compression ignition#Gelling|Compression Ignition – Gelling]]) that cannot flow in fuel systems. Special [[Winter diesel fuel|low-temperature diesel]] contains additives to keep it liquid at lower temperatures.

=== On-road vehicles ===

[[Truck]]s and [[bus]]es, which were often otto-powered in the 1920s through 1950s, are now almost exclusively diesel-powered. Due to its ignition characteristics, diesel fuel is thus widely used in these vehicles. Since diesel fuel is not well-suited for otto engines, passenger cars, which often use otto or otto-derived engines, typically run on petrol instead of diesel fuel. However, especially in Europe and India, many passenger cars have, due to better engine efficiency,<ref name="argus">{{cite news|last=Nadel|first=Norman|date=11 May 1977|title=Diesel Revival Is Going On in the Motor City|url=https://news.google.com/newspapers?nid=1988&dat=19770511&id=AUUiAAAAIBAJ&pg=1245,1255941|newspaper=[[The Argus-Press]]|location=[[Detroit|Detroit, Michigan]]|access-date=28 July 2014}}</ref> diesel engines, and thus run on regular diesel fuel.

=== Railroad ===
{{See also|Dieselisation|Diesel locomotive}}
Diesel displaced coal and fuel oil for steam-powered vehicles in the latter half of the 20th century, and is now used almost exclusively for the combustion engines of self-powered rail vehicles (locomotives and railcars).<ref>{{cite book |last1=Solomon|first1=Brian|last2=Yough|first2=Patrick|date=15 July 2009|title=Coal Trains: The History of Railroading and Coal in the United States (Google eBook)|url=https://books.google.com/books?id=oAIiJCH4Kw8C&q=diesel+in+trains+coal|publisher=MBI Publishing Company|isbn=978-0-7603-3359-4|access-date=9 October 2014}}</ref><ref>{{cite book |last=Duffy|first=Michael C.|date=1 January 2003|title=Electric Railways 1880–1990|url=https://books.google.com/books?id=cpFEm3aqz_MC&q=diesel+in+trains+coal+uk|location=London|publisher=Institution of Engineering and Technology|isbn=978-0-85296-805-5|access-date=9 October 2014}}</ref>

=== Aircraft ===
[[file:Packard DR-980 USAF.jpg|thumb|Packard DR-980 9-cylinder diesel aircraft engine, used in the first diesel-engine airplane]]

In general, diesel engines are not well-suited for planes and helicopters. This is because of the diesel engine's comparatively low [[power-to-weight ratio|power-to-mass ratio]], meaning that diesel engines are typically rather heavy, which is a disadvantage in aircraft. Therefore, there is little need for using diesel fuel in aircraft, and diesel fuel is not commercially used as aviation fuel. Instead, petrol ([[Avgas]]), and [[jet fuel]] (e. g. Jet A-1) are used. However, especially in the 1920s and 1930s, numerous series-production aircraft diesel engines that ran on fuel oils were made, because they had several advantages: their fuel consumption was low, they were reliable, not prone to catching fire, and required minimal maintenance. The introduction of petrol direct injection in the 1930s outweighed these advantages, and aircraft diesel engines quickly fell out of use.<ref>Konrad Reif: ''Dieselmotor-Management – Systeme, Komponenten, Steuerung und Regelung'', 5th edition, Springer, Wiesbaden 2012, {{ISBN|978-3-8348-1715-0}}, p. 103</ref> With improvements in power-to-mass ratios of diesel engines, several on-road diesel engines have been converted to and certified for aircraft use since the early 21st century. These engines typically run on [[Jet A-1]] aircraft fuel (but can also run on diesel fuel). Jet A-1 has ignition characteristics similar to diesel fuel, and is thus suited for certain (but not all) diesel engines.<ref>Cord-Christian Rossow, Klaus Wolf, Peter Horst: ''Handbuch der Luftfahrzeugtechnik'', Carl Hanser Verlag, 2014, {{ISBN|9783446436046}}, p. 519</ref>

=== Military vehicles ===

Until World War II, several military vehicles, especially those that required high engine performance ([[armored fighting vehicle]]s, for example the [[M26 Pershing]] or [[Panther tank|Panther]] tanks), used conventional otto engines and ran on petrol. Ever since World War II, several military vehicles with diesel engines have been made, capable of running on diesel fuel. This is because diesel engines are more fuel efficient, and diesel fuel is less prone to catching fire.<ref>{{cite book
  |chapter=Engines for Main Battle Tanks
  |title=Jane's 1981–82 Military Annual
  |last=Tillotson
  |first=Geoffrey
  |editor=Col. John Weeks
  |publisher=[[Jane's]]
  |isbn=978-0-7106-0137-7
  |year=1981
  |page=59,63
}}</ref> Some of these diesel-powered vehicles (such as the [[Leopard 1]] or [[MAN 630]]) still ran on petrol, and some military vehicles were still made with otto engines (e. g. [[Ural-375]] or [[Unimog 404]]), incapable of running on diesel fuel.

=== Tractors and heavy equipment ===

Today's [[tractor]]s and [[heavy equipment]] are mostly diesel-powered. Among tractors, only the smaller classes may also offer gasoline-fuelled engines. The [[dieselization]] of tractors and heavy equipment began in Germany before World War II but was unusual in the United States until after that war. During the 1950s and 1960s, it progressed in the US as well. Diesel fuel is commonly used in oil and gas extracting equipment, although some locales use electric or natural gas powered equipment.

Tractors and heavy equipment were often [[multifuel]] in the 1920s through 1940s, running either spark-ignition and low-compression engines, akryod engines, or diesel engines. Thus many farm tractors of the era could burn gasoline, [[ethanol fuel|alcohol]], [[kerosene]], and any light grade of [[fuel oil]] such as [[heating oil]], or [[tractor vaporising oil]], according to whichever was most affordable in a region at any given time. On US farms during this era, the name "distillate" often referred to any of the aforementioned light fuel oils. Spark ignition engines did not start as well on distillate, so typically a small auxiliary gasoline tank was used for cold starting, and the fuel valves were adjusted several minutes later, after warm-up, to transition to distillate. Engine accessories such as [[carburetor#Vaporizers|vaporizers]] and [[radiator (engine cooling)#Radiator blind|radiator shrouds]] were also used, both with the aim of capturing heat, because when such an engine was run on distillate, it ran better when both it and the air it inhaled were warmer rather than at ambient temperature. Dieselization with dedicated diesel engines (high-compression with mechanical fuel injection and compression ignition) replaced such systems and made more [[engine efficiency|efficient]] use of the diesel fuel being burned.

=== Other uses ===
Poor quality diesel fuel has been used as an extraction agent for [[liquid–liquid extraction]] of [[palladium]] from [[nitric acid]] mixtures.<ref name="chemabstracts">{{cite book|author=<!--Staff writer(s); no by-line.-->|title=Chemical Abstracts|url=https://books.google.com/books?id=AGMcAQAAMAAJ&q=high+sulfur+diesel+fuel+palladium+nitric+acid+liquid-liquid+extraction|volume=110|location=Washington D.C.|publisher=American Chemical Society|date=13 March 1989|access-date=28 July 2014}}</ref> Such use has been proposed as a means of separating the [[fission product]] palladium from [[PUREX]] [[raffinate]] which comes from used [[nuclear fuel]].<ref name="chemabstracts" /> In this system of solvent extraction, the [[hydrocarbon]]s of the diesel act as the [[diluent]] while the di[[alkyl]] [[sulfide]]s act as the extractant.<ref name="chemabstracts" /> This extraction operates by a [[solvation]] mechanism.<ref name="chemabstracts" /> So far, neither a [[pilot plant]] nor full scale plant has been constructed to recover palladium, [[rhodium]] or [[ruthenium]] from [[nuclear waste]]s created by the use of [[nuclear fuel]].<ref>Torgov, V.G.; Tatarchuk, V.V.; Druzhinina, I.A.; Korda, T.M. ''et al.'', ''Atomic Energy'', 1994, '''76'''(6), 442–448. (Translated from Atomnaya Energiya; 76: No. 6, 478–485 (June 1994))</ref>

Diesel fuel is often used as the main ingredient in oil-base mud drilling fluid.<ref name="eisbdf">{{cite report|author1=Neff, J.M.|author2=McKelvie, S.|author3=Ayers, RC Jr.|date=August 2000|title=Environmental Impacts of Synthetic Based Drilling Fluids|url=http://www.anp.gov.br/brnd/round6/guias/PERFURACAO/PERFURACAO_R6/biblio/fluido%20sintetico.pdf|publisher=U.S. Department of the Interior Minerals Management Service|pages=1–4|docket=2000-064|access-date=28 July 2014|url-status=dead|archive-url=https://web.archive.org/web/20140728233206/http://www.anp.gov.br/brnd/round6/guias/PERFURACAO/PERFURACAO_R6/biblio/fluido%20sintetico.pdf|archive-date=28 July 2014}}</ref> The advantage of using diesel is its low cost and its ability to drill a wide variety of difficult strata, including shale, salt and gypsum formations.<ref name="eisbdf" /> Diesel-oil mud is typically mixed with up to 40% brine water.<ref name="bfaf">{{cite web|url=http://gekengineering.com/Downloads/Free_Downloads/Brines_fluids_and_filtration.pdf|title=Brines and Other Workover Fluids|author=<!--Staff writer(s); no by-line.-->|date=14 March 2009|website=GEKEngineering.com|publisher=George E. King Engineering|access-date=28 July 2014|archive-url=https://web.archive.org/web/20131020111636/http://gekengineering.com/Downloads/Free_Downloads/Brines_fluids_and_filtration.pdf|archive-date=2013-10-20|url-status=dead}}</ref> Due to health, safety and environmental concerns, Diesel-oil mud is often replaced with vegetable, mineral, or synthetic food-grade oil-base drilling fluids, although diesel-oil mud is still in widespread use in certain regions.<ref>{{cite web |work=Schlumberger Oil Field Glossary |title=diesel-oil mud |archive-url=https://web.archive.org/web/20040122220559/http://www.glossary.oilfield.slb.com/Display.cfm?Term=diesel-oil%20mud |archive-date=22 January 2004 |url=http://www.glossary.oilfield.slb.com/Display.cfm?Term=diesel-oil%20mud}}</ref>

During development of rocket engines in [[Germany]] during [[World War II]] J-2 Diesel fuel was used as the fuel component in several engines including the [[BMW 109-718]].<ref name=CIOSCBMW /> J-2 diesel fuel was also used as a fuel for gas turbine engines.<ref name=CIOSCBMW>{{cite web|last1=Price|first1=P.R, Flight Lieutenant|title=Gas turbine development by BMW|url=http://www.cdvandt.org/CIOS-XXVI-30.pdf|publisher=Combined Intelligence Objectives Sub-Committee|access-date=7 June 2014}}</ref>

== Chemical analysis ==

=== Chemical composition ===
[[File:Dieselrainbow.jpg|thumb|right|Diesel [[immiscible|does not mix]] with water. This picture also showcases the phenomenon of [[Thin-film interference]].]]
In the United States, petroleum-derived diesel is composed of about 75% [[saturated hydrocarbon]]s (primarily [[Alkane|paraffins]] including [[Isoparaffin#Linear alkanes|''n'']], [[Isoalkane#Isomerism|''iso'']], and [[Cycloalkane|cycloparaffins]]), and 25% [[aromatic hydrocarbon]]s (including [[naphthalene]]s and [[alkylbenzenes]]).<ref>Agency for Toxic Substances and Disease Registry (ATSDR). 1995. ''[http://www.atsdr.cdc.gov/toxprofiles/tp75-c3.pdf Toxicological profile for fuel oils]''. Atlanta, GA: [[United States Department of Health and Human Services|U.S. Department of Health and Human Services]], Public Health Service</ref> The average chemical formula for common diesel fuel is C<sub>12</sub>H<sub>23</sub>, ranging approximately from C<sub>10</sub>H<sub>20</sub> to C<sub>15</sub>H<sub>28</sub>.<ref>{{cite book|last=Date|first=Anil W.|date=7 March 2011|title=Analytic Combustion: With Thermodynamics, Chemical Kinetics and Mass Transfer (Google eBook)|url=https://books.google.com/books?id=uPZXiVTCEcIC&q=chemical+composition+of+diesel+fuel+c12h23,+c10h20,+c15h28|publisher=Cambridge University Press|page=189|isbn=978-1-107-00286-9|access-date=9 October 2014}}</ref>

=== Chemical properties ===
{{further|Diesel exhaust|Gel point (petroleum)}}
Most diesel fuels freeze at common winter temperatures, while the temperatures greatly vary.<ref name="nrel" /> Petrodiesel typically freezes around temperatures of {{convert|-8.1|°C|°F|abbr=on}}, whereas biodiesel freezes between temperatures of {{convert|2|to|15|C|F}}.<ref name="nrel">{{cite report|author=National Renewable Energy Laboratory staff|date=January 2009|title=Biodiesel Handling and Use Guide|url=http://www.biodiesel.org/docs/using-hotline/nrel-handling-and-use.pdf?sfvrsn=4|publisher=National Renewable Energy Laboratory|edition=Fourth|page=10|docket=NREL/TP-540-43672|access-date=18 July 2014|archive-url=https://web.archive.org/web/20160306103447/http://biodiesel.org/docs/using-hotline/nrel-handling-and-use.pdf?sfvrsn=4|archive-date=6 March 2016|url-status=dead}}</ref> The viscosity of diesel noticeably increases as the temperature decreases, changing it into a gel at temperatures of {{convert|-19|to|-15|°C|°F|abbr=on}}, that cannot flow in fuel systems. Conventional diesel fuels vaporise at temperatures between 149&nbsp;°C and 371&nbsp;°C.<ref name="ufa1">{{cite web|url=https://www.staroilco.net/diesel-fuel-technical-review-from-chevron/|title=Diesel Fuel Technical Review|author=<!--Staff writer(s); no by-line.-->|year=2007|website=www.staroilco.net|publisher=Chevron}}</ref>

Conventional diesel [[flash point]]s vary between 52 and 96&nbsp;°C, which makes it safer than petrol and unsuitable for spark-ignition engines.<ref name=gasfp>{{cite web |url= http://www.engineeringtoolbox.com/flash-point-fuels-d_937.html|title= Flash Point — Fuels|access-date=January 4, 2014}}</ref> Unlike petrol, the flash point of a diesel fuel has no relation to its performance in an engine nor to its auto ignition qualities.<ref name="ufa1" />

== Carbon dioxide formation ==
As a good approximation the chemical formula of diesel is {{chem|C|n|H|2n}}. Diesel is a mixture of different molecules. As carbon has a molar mass of 12 g/mol and hydrogen has a molar mass of about 1 g/mol, so the fraction by weight of carbon in EN&nbsp;590 diesel fuel is roughly 12/14.

The reaction of diesel combustion is given by:

2{{chem|C|n|H|2n}} + 3n{{chem|O|2}} {{eqm}} 2n{{chem|C|O|2}} + 2n{{chem|H|2|O}}

Carbon dioxide has a molar mass of 44g/mol as it consists of 2 atoms of oxygen (16 g/mol) and 1 atom of carbon (12 g/mol). So 12 g of carbon yield 44 g of Carbon dioxide.

Diesel has a density of 838&nbsp;g per liter.

Putting everything together the mass of carbon dioxide that is produced by burning 1 liter of diesel fuel can be calculated as:

<math>0.838 kg/L \cdot {\frac{12}{14}}\cdot {\frac{44}{12}}= 2.63 kg/L</math>

The figure obtained with this estimation is close to the values found in the literature.

For gasoline, with a density of 0.75&nbsp;kg/L and a ratio of carbon to hydrogen atoms of about 6 to 14, the estimated value of carbon emission if 1 liter of gasoline is burnt gives:<ref>{{cite book |last=Hilgers |first=Michael |title=Dieselmotor |publisher=Springer |year=2016 |isbn=978-3-658-14641-2 |location=Wiesbaden |pages=6}}</ref>

<math> 0.75 kg/L \cdot {\frac{6 \cdot 12}{6\cdot 12 + 14}\cdot 1} \cdot {\frac{44}{12}}= 2.3 kg/L </math>

== Hazards ==
{{See also|diesel exhaust}}

=== Environment hazards of sulfur ===

In the past, diesel fuel contained higher quantities of [[sulfur]]. [[European emission standards]] and preferential taxation have forced [[oil refinery|oil refineries]] to dramatically reduce the level of sulfur in diesel fuels. In the European Union, the sulfur content has dramatically reduced during the last 20 years. Automotive diesel fuel is covered in the European Union by standard [[EN 590]]. In the 1990s specifications allowed a content of 2000 ppm max of sulfur, reduced to a limit of 350 ppm by the beginning of the 21st century with the introduction of Euro 3 specifications. The limit was lowered with the introduction of Euro 4 by 2006 to 50 ppm ([[ULSD]], Ultra Low Sulfur Diesel). The standard for diesel fuel in force in Europe as of 2009 is the Euro 5, with a maximum content of 10 ppm.<ref>{{cite web|url=https://www.transportpolicy.net/standard/eu-fuels-diesel-and-gasoline/|title= EU: Fuels: Diesel and Gasoline|website=TransportPolicy.net|access-date=17 July 2020}}</ref>

{| class="wikitable"
! Emission standard
! At latest
! Sulfur content
! Cetane number
|-
| N/a
|align=right| 1 January 1994
|align=right| max. 2000 ppm
|align=right| min. 49
|-
| Euro 2
|align=right| 1 January 1996
|align=right| max. 500 ppm
|align=right| min. 49
|-
| Euro 3
|align=right| 1 January 2001
|align=right| max. 350 ppm
|align=right| min. 51
|-
| Euro 4
|align=right| 1 January 2006
|align=right| max. 50 ppm
|align=right| min. 51
|-
| Euro 5
|align=right| 1 January 2009
|align=right| max. 10 ppm
|align=right| min. 51
|-
|}

In the United States, more stringent emission standards have been adopted with the transition to  [[Ultra-low-sulfur diesel|ULSD]] starting in 2006, and becoming mandatory on June 1, 2010 (see also [[diesel exhaust]]).

=== Algae, microbes, and water contamination ===
{{main|microbial contamination of diesel fuel}}
There has been much discussion and misunderstanding of [[algae]] in diesel fuel. Algae need light to live and grow. As there is no sunlight in a closed fuel tank, no algae can survive, but some [[microbes]] can survive and feed on the diesel fuel.<ref>{{cite web|url=http://criticalfueltech.com/faq.html|title=What is Diesel Fuel "ALGAE"?|author=<!--Staff writer(s); no by-line.-->|year=2012|website=criticalfueltech.com|publisher=Critical Fuel Technology, Inc.|access-date=9 October 2014}}</ref>

These microbes form a colony that lives at the interface of fuel and water. They grow quite fast in warmer temperatures. They can even grow in cold weather when fuel tank heaters are installed. Parts of the colony can break off and clog the fuel lines and fuel filters.<ref>{{cite tech report|title=Microbial Contamination of Diesel Fuel: Impact, Causes and Prevention|number=253-01246|institution=Dow Chemical Company|year=2003}}</ref>

Water in fuel can damage a fuel [[injection pump]]. Some diesel [[fuel filter]]s also trap water. Water contamination in diesel fuel can lead to freezing while in the fuel tank. The freezing water that saturates the fuel will sometimes clog the fuel injector pump.<ref>{{cite web|url=http://www.afssociety.org/automotive/93-water-contamination-in-fuel-cause-and-effect|title=Water Contamination in Fuel: Cause and Effect - American Filtration and Separations Society|author=AFS admin|url-status=dead|archive-url=https://web.archive.org/web/20150323111230/http://www.afssociety.org/automotive/93-water-contamination-in-fuel-cause-and-effect|archive-date=2015-03-23}}</ref> Once the water inside the fuel tank has started to freeze, gelling is more likely to occur. When the fuel is gelled it is not effective until the temperature is raised and the fuel returns to a liquid state.

=== Road hazard ===
Diesel is less flammable than [[Gasoline|gasoline / petrol]]. However, because it evaporates slowly, any spills on a roadway can pose a slip hazard to vehicles.<ref>{{cite web|title=Oil on the road as a cause of accidents|url=http://www.icbcclaiminfo.com/node/23|publisher=ICBCclaiminfo.com|url-status=dead|archive-url=https://web.archive.org/web/20130407043946/http://www.icbcclaiminfo.com/node/23|archive-date=7 April 2013}}</ref> After the light fractions have evaporated, a greasy slick is left on the road which reduces [[tire]] grip and traction, and can cause vehicles to skid. The loss of traction is similar to that encountered on [[black ice]], resulting in especially dangerous situations for two-wheeled vehicles, such as [[motorcycle]]s and [[bicycle]]s, in [[roundabout]]s.

== See also ==
{{portal|Energy}}
{{div col|colwidth=30em}}
* [[Common ethanol fuel mixtures]]
* [[Biodiesel]]
* [[Diesel automobile racing]]
* [[Dieselisation]]
* [[Gasoline]]
* [[Gasoline gallon equivalent]]
* [[Hybrid vehicle]]
* [[Liquid fuel]]
* [[List of diesel automobiles]]
* [[Turbo-diesel]]
* ''[[United States v. Imperial Petroleum, Inc.]]''
* [[Winter diesel fuel]]
{{div col end}}

== References ==
{{Reflist}}

== External links ==
{{Commons category|Diesel}}
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* [https://www.osha.gov/SLTC/dieselexhaust/ U.S. Department of Labor Occupational Safety & Health Administration: Safety and Health Topics: Diesel Exhaust]

{{Motor fuel}}
{{Authority control}}

[[Category:Diesel fuel| ]]
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