Ethanol is a non-refinery based hydrocarbon that is used as a gasoline blend stock.

Ethanol is blended into gasoline for a variety of business and policy reasons. Ethanol has high octane and can be used as an octane booster. Because ethanol contains oxygen, it can be used to reduce the carbon monoxide emissions from burning gasoline. Also, as a renewable fuel, ethanol blending is mandated in some markets to reduce reliance on fossil fuels.

Ethanol is manufactured by fermenting the sugars in agricultural products such as corn, sugar cane and beets. As such, it is able to receive bio-fuel credits in countries with these regulations.

When blended into gasoline, Ethanol significantly raises the octane and vapor pressure. However, its impact on both qualities varies widely with the concentration of ethanol in the mix and the chemical properties of the other hydrocarbons in the blend. As a result, ethanol is typically blended into gasoline in fixed ratios (e.g., 10%, 15%), and ethanol blended gasoline is kept segregated from ethanol-free gasoline.