page_title: Common ethanol fuel mixtures
section_title: E100
hierarchical_section_title: Common ethanol fuel mixtures / E100
caption_attribution_description: English: {{Information FlexPower engine with secondary gasoline reservoir for cold starting, Brazilian flexible-fuel Chevrolet Celta}}
context_page_description: Several common ethanol fuel mixtures are in use around the world. The use of pure hydrous or anhydrous ethanol in internal combustion engines is only possible if the engines are designed or modified for that purpose, and used only in automobiles, light-duty trucks and motorcycles. Anhydrous ethanol can be blended with gasoline for use in gasoline engines, but with high ethanol content only after minor engine modifications.
  Ethanol fuel mixtures have "E" numbers which describe the percentage of ethanol fuel in the mixture by volume, for example, E85 is 85% anhydrous ethanol and 15% gasoline. Low-ethanol blends, from E5 to E25, although internationally the most common use of the term refers to the E10 blend.
  Blends of E10 or less are used in more than 20 countries around the world, led by the United States, where ethanol represented 10% of the U.S. gasoline fuel supply in 2011. Blends from E20 to E25 have been used in Brazil since the late 1970s. E85 is commonly used in the U.S. and Europe for flexible-fuel vehicles. Hydrous ethanol or E100 is used in Brazilian neat ethanol vehicles and flex-fuel light vehicles and hydrous E15 called hE15 for modern petrol cars in the Netherlands.
context_section_description: E100 is pure ethanol fuel. Straight hydrous ethanol as an automotive fuel has been widely used in Brazil since the late 1970s for neat ethanol vehicles and more recently for flexible-fuel vehicles. The ethanol fuel used in Brazil is distilled close to the azeotrope mixture of 95.63% ethanol and 4.37% water (by weight) which is approximately 3.5% water by volume.
  The azeotrope is the highest concentration of ethanol that can be achieved by simple fractional distillation.  The maximum water concentration according to the ANP specification is 4.9 vol.% (approximately 6.1 weight%)  The E nomenclature is not adopted in Brazil, but hydrated ethanol can be tagged as E100, meaning it does not have any gasoline, because the water content is not an additive, but rather a residue from the distillation process. However,  straight hydrous ethanol is also called E95 by some authors.
  The first commercial vehicle capable of running on pure ethanol was the Ford Model T, produced from 1908 through 1927. It was fitted with a carburetor with adjustable jetting, allowing use of gasoline or ethanol, or a combination of both. At that time, other car manufacturers also provided engines for ethanol fuel use. Thereafter, and as a response to the 1973 and 1979 energy crises, the first modern vehicle capable of running with pure hydrous ethanol (E100) was launched in the Brazilian market, the Fiat 147, after testing with several prototypes developed by the Brazilian subsidiaries of Fiat, Volkswagen, General Motors and Ford. As of September 2012, there were 1.1 million neat ethanol vehicles still in use in Brazil. Since 2003, Brazilian newer flex-fuel vehicles are capable of running on pure hydrous ethanol (E100) or blended with any combination of E20 to E27.5 gasoline (a mixture made with anhydrous ethanol), the national mandatory blend. As of September 2012, there were 17.1 million flexible-fuel vehicles running on Brazilian roads.
  E100 imposes a limitation on normal vehicle operation, as ethanol's lower evaporative pressure (as compared to gasoline) causes problems when cold starting the engine at temperatures below 15 °C (59 °F). For this reason, both pure ethanol and E100 flex-fuel vehicles are built with an additional small gasoline reservoir inside the engine compartment to help in starting the engine when cold by initially injecting gasoline.  Once started, the engine is then switched back to ethanol. An improved flex-fuel engine generation was developed to eliminate the need for the secondary gas tank by warming the ethanol fuel during starting, and allowing them to start at temperatures as low as −5 °C (23 °F), the lowest temperature expected anywhere in the Brazilian territory. The Polo E-Flex, launched in March 2009, was the first flex-fuel model without an auxiliary tank for cold start. The warming system, called Flex Start, was developed by Robert Bosch GmbH.
  Swedish carmakers have developed ethanol-only capable engines for the new Saab Aero X BioPower 100 Concept E100, with a V6 engine which is fuelled entirely by E100 bioethanol, and the limited edition of the Koenigsegg CCXR, a version of the CCX converted to use E85 or E100, as well as standard 98-octane gasoline, and currently the fastest and most powerful flex-fuel vehicle with its twin-supercharged V8 producing 1018 hp when running on biofuel, as compared to 806 hp on 91-octane unleaded gasoline.
  The higher fuel efficiency of E100 (compared to methanol) in high performance race cars resulted in Indianapolis 500 races in 2007 and 2008 being run on 100% fuel-grade ethanol.
caption: Typical Brazilian flexible-fuel engine with secondary gasoline reservoir for cold starting the engine at temperatures below 15 °C (59 °F)
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