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Frequently Asked Questions (FAQs)

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

Most of finished motor gasoline sold in the United States is about 10% fuel ethanol by volume. In 2023, about 0.33 billion barrels (13.73 billion gallons) of fuel ethanol were blended into the 3.26 billion barrels (137.11 billion gallons) of finished motor gasoline consumed. Fuel ethanol contains a denaturant that is added to ethanol to make fuel ethanol unfit for human consumption. Federal law requires that fuel ethanol contain at least 2% denaturant by volume, but the actual amount in fuel ethanol may be higher.

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. Most of finished motor gasoline sold in the United States is E10. E15 is gasoline with 15% ethanol content, and E85 is a fuel that may contain up to 85% fuel ethanol. Most motor gasoline with more than 10% fuel ethanol content is sold in the Midwest where most 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 newer are approved by the EPA to use E15. 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:
Biofuels Explained: Ethanol
Fuel ethanol overview (Table 10.3). Contains fuel ethanol consumption data.
U.S. Petroleum Supply and Disposition
Articles on ethanol
Issues and Methods for Estimating the Share of Ethanol in the Motor Gasoline Supply

Last updated: April 1, 2024.

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