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What is a Flex-Fuel?

Flex, or flexible fuel, is an alternative renewable fuel with a combination of petrol and different types of concentrated ethanol, or methanol. The extraction of bioethanol is from sugar, residual crops, or other biomass. Flex fuel vehicle is the alternative fuel-adaptive vehicle. Flex Fuel Vehicles (FFV) have spread throughout the automotive industry during the past 20 years and offer customers a fuel choice other than traditional gasoline.

What to know about Flex Fuel


‘E10’ fuel is about 5 to 10 percent ethanol-petrol blend. Currently, most vehicles manufactured after 2008 can support E10 without much difficulty. In 2008, the Society of Indian Automobile Manufacturers (SIAM) set up fuel material compatibility countermeasures for vehicles manufactured from 2008 onwards.


Any Flex Fuel vehicles or vehicles with a 2001 model year and newer are approved to use E15. Motorcycles, heavy-duty vehicles, motorsport vehicles and vehicles older than 2001 are not authorised to use E15. The EPA has approved another blend, E15, in all light-duty cars since 2001. Manufacturers responsible for nearly 95% of U.S. light-duty vehicle sales endorse the use of E15 in their model year 2022 automobiles, according to a review of owner’s manuals by the trade group RFA.


E25 contains 25% ethanol. This blend has been widely used in Brazil since the late 1970s. In 2022, BMW and Mini go a step further by approving the use of gasoline containing up to 25% ethanol (E25) in the latest model.


E85 is a gasoline-ethanol blend containing between 51% and 85% ethanol. It depends on the season and geographic region of the distributor. E85 sold during colder months often has lower levels of ethanol to produce the vapour pressure necessary for starting the engine in cold temperatures.


E98, or 98% ethanol, is a popular fuel for some types of race cars. Consistency of the energy is also paramount as most ethanol available at retail dispensers can contain 70–90% ethanol. The stoichiometric ratio for ethanol is 9.0:1. E98 can be used as a race fuel or blended with other gasoline to achieve the desired ethanol concentration. This product is designed to meet ASTM standard D4806 standard specification for Denatured Fuel Ethanol for blending with gasoline.

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