Frequently Asked Questions

How much ethanol is in gasoline, and how does it affect fuel economy?

In 2014, more than 13 billion gallons of fuel ethanol were added to motor gasoline produced in the United States, and fuel ethanol accounted for about 10% of the total volume of finished motor gasoline consumed in the United States. Fuel ethanol contains a denaturant that is added to ethanol to make the ethanol unfit for human consumption. Federal law requires fuel ethanol to contain at least 2% denaturant by volume, but the actual content in fuel ethanol may be higher.

Most of the gasoline now sold in the United States contains some ethanol. Most of ethanol blending into U.S. motor gasoline occurs to meet the requirements of the 1990 Clean Air Act (RFG Fuel) and the Renewable Fuel Standard set forth in the Energy Independence and Security Act of 2007. The U.S. Environmental Protection Agency (EPA) administers the requirements with the Renewable Fuel Standard Program.

There are three general categories of ethanol-gasoline blends: E10, E15, and E85. E10 is gasoline with 10% ethanol content; E15 is gasoline with 15% ethanol content; and E85 is a fuel that may contain up to 85% fuel ethanol. The ethanol content of most of the motor gasoline sold in the United Sates does not exceed 10% by volume. Most of the motor gasoline with more than 10% fuel ethanol content is sold in the Midwest, where most of ethanol production capacity is located. Gasoline dispensing pumps generally indicate the fuel ethanol content of the gasoline.

All gasoline engine vehicles can use E10. Currently, only flex-fuel and light-duty vehicles with a model year of 2001 or greater are approved by the EPA to use E15, although some automakers have yet to approve the use of E15 in their vehicles. Flex-fuel vehicles can use any ethanol-gasoline blends up to E85.

The energy content of ethanol is about 33% less than pure gasoline. The impact of fuel ethanol on vehicle fuel economy varies depending on the amount of denaturant that is added to the ethanol. The energy content of denaturant is about equal to the energy content of pure gasoline. In general, vehicle fuel economy may decrease by about 3% when using E10 relative to gasoline that does not contain fuel ethanol.

Learn more:

Ethanol Fuel Basics

U.S. petroleum supply and disposition

Articles on ethanol

Issues and Methods for Estimating the Share of Ethanol in the Motor Gasoline Supply

Biofuels Issues and Trends

Last updated: December 1, 2015


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