E85 is a corn-based ethanol fuel produced within the United States. While E85 is usually cheaper than gasoline, it should only be used in cars that have been designed or retrofitted for E85. Attempting to use E85 in a vehicle not designed to burn E85 will result in poor performance, and will likely cause engine component damage.
E85 contains 85 percent denatured fuel ethanol and 15 percent conventional petroleum fuel. E85 -- which is part of the effort to reduce U.S. dependency on foreign oil -- is produced domestically by processing corn, and is thus a renewable energy source. The U.S. Department of Energy states that E85 produces lower carbon monoxide and carbon dioxide emissions as compared to traditional petroleum fuels.
Vehicles that are built to safely run E85 will be called flex-fuel vehicles by the manufacturer. There should be a flex-fuel decal placed on the fuel door, or by the vehicle identification number. Many manufacturers, such as Ford and General Motors, produce flex-fuel versions of their popular models. To safely run E85, these cars usually have modified fuel-delivery systems and fuel sensors.
There are two problems with running E85 in a car that's not prepped for E85. First, E85 is more corrosive than traditional petroleum fuels and thus will cause damage to rubber components, such as fuel lines, in a vehicle not designed for E85.
Second, E85 contains less energy per volume compared to petroleum. This means that unless the car's engine computer has been programmed to run E85, the computer will be unable to compensate fully for the reduced-energy E85 fuel, causing lean running conditions, misfires and thus subjecting pistons and valves to greater stress and wear.
