Ethanol is blended with gasoline at rates of 10 percent to 85 percent for U.S. motor fuel. Only flexible-fuel vehicles can burn higher-ratio blends. Here is a look at the differences.
E10: The standard U.S. motor fuel with 10 percent ethanol, in use for decades.
E15: Possibly the next standard U.S. motor fuel. The Environmental Protection Agency has approved the 15 percent ethanol blend for 2001-and-newer cars and light trucks. Automakers say these vehicles have not been sufficiently tested with E15 and that warranties may not cover damage attributed to the fuel. E15 is not permitted for use in pre-2001 cars and trucks, or in off-road vehicles, motorcycles, or engines on boats and lawn and garden equipment. E15 sales could begin as early as next month.
E20: The 20 percent ethanol blend can only be purchased at stations with blender pumps for use in flexible-fuel vehicles. Some ethanol advocates see E20 as a standard motor fuel in the future, however.
E85: Blends of up to 85 percent alcohol can be burned only in flex-fuel vehicles. The actual ratio will vary between 51 percent to 83 percent depending on region. Fuel economy is about 25 percent lower than with E10.Sources: U.S. Department of Energy, Environmental Protection Agency