E85 is an abbreviation for an ethanol fuel blend of up to 85% denatured ethanol fuel and gasoline or other hydrocarbon by volume. E85 is commonly used by flex-fuel vehicles in the United States and Europe. In the United States, government promotion of ethanol in general and E85 in particular has encouraged a growing infrastructure for retail sale of E85, especially in corn growing states in the Midwest.

E85 has a number of advantages over conventional gasoline. One advantage is a reduction in tailpipe emissions. Another advantage is a high effective octane rating, reducing engine heat and wear, and increasing performance. Because the ethanol component effectively displaces fossil fuels with energy harvested from renewable sources, in theory E85 is less carbon intensive than petroleum. Additionally, there is a greater potential for localized production of ethanol in agricultural areas and using waste materials. Also, a diversification of fuel sources reduces dependence on a particular type of fuel and may increase stability of supply.