Ethanol is added to gasoline because it is a renewable source of energy and helps to decrease carbon emissions and reduce America's energy dependence on other countries. It also acts as an oxygenating agent, which reduces carbon monoxide and soot emissions produced when fossil fuels are burned. The United States government mandates the addition of ethanol or other biofuels to gasoline as part of the Energy Policy Act and Renewable Fuels Standard.
Until the 1970s, most gasoline products contained lead as an additive. The United States began reducing the use of lead, replacing it with methyl tert-butyl ether as an oxygenating additive. After most states banned the use of MTBE for polluting ground water and for other health and environmental concerns, ethanol replaced MTBE as the primary oxygenating agent in gasoline. Ethanol gasoline also helps keep a vehicle's fuel system cleaner longer than leaded gasoline.
Ethanol is primarily a corn derivative. The exact amount of ethanol added to gasoline varies from state to state, but it does not exceed 10 percent for gasoline for regular vehicles. Only Flex Fuel vehicles can run on gasoline with a higher percentage of ethanol. Henry Ford originally intended his Model T to run on alcohol derived from corn.