E85 is an abbreviation for flex fuel meaning a mixture of up to 85% denatured fuel ethanol and gasoline or other hydrocarbon (HC) by volume.

Some of the benefits of E85 over conventional gasoline powered vehicles include the potential for localized production of fuel in agricultural areas. Another benefit is potentially reduced pollution emissions especially Carbon dioxide in Earth's atmosphere which is an important element for adaptation to global warming.

Potential benefits of E85 are contested by some experts who point out that deriving gasoline from petroleum is a relatively inexpensive (i.e., more efficient) process, even including the transportation of oil and gasoline long distances. Large-scale production of ethanol may be cost-prohibitive; and may result in a net energy loss when taking into account all the energy required to make alcohol from starchy plants. Another drawback for E85 is that, in a liter-to-liter comparison, E85 has less power potential than conventional gasoline; 30% percent less energy for transportation by volume.