A flex-fuel vehicle is one whose engine is designed to run on full-concentration gasoline or a gasoline-ethanol blend. The gas tank can store both types of fuel in any amount, allowing drivers to choose the cheaper fuel option.
Ethanol blends typically give drivers less mileage per gallon, but do not significantly alter engine power or acceleration. Ethanol is also thought to decrease dependence on foreign oil by reducing the amount of pure gasoline needed to fill each tank. In addition to being a domestic product, ethanol also releases fewer greenhouse gas emissions, making it a more sustainable and environmentally friendly fuel choice.