Gasoline—a petroleum product
Gasoline is a fuel made from crude oil and other petroleum liquids. Gasoline is mainly used as an engine fuel in vehicles. Refineries and companies that produce the finished motor gasoline sold in retail gasoline fueling stations may add various liquids so that the gasoline burns cleaner and meets air pollution control standards and requirements.
Finished motor gasoline meets the basic requirements for fuel that is suitable for use in spark ignition engines. Some finished motor gasoline may require additional blending with ethanol (a renewable fuel and oxygenate), detergents and other additives, and higher octane gasoline before it is delivered to retail outlets for sale to end users. Most of the gasoline that oil refineries produce is actually unfinished gasoline (or gasoline blendstocks). Gasoline blendstocks require additional blending and usually require ethanol before delivery to retail outlets as finished gasoline. Refineries produce some finished gasoline, but most of the finished gasoline sold in the United States is actually produced at blending terminals where finished gasoline, gasoline blendstocks, and fuel ethanol are processed into finished gasoline ready for consumer use. Blending terminals are more numerous and widely dispersed than refineries, and they have equipment for loading trucks that transport finished gasoline to retail outlets.
Most of the motor gasoline now sold in the United States contains about 10% fuel ethanol by volume. Ethanol is added to gasoline mainly to meet the requirements of the Renewable Fuels Standard, which is intended to reduce greenhouse gas emissions and the amount of oil that the United States imports from other countries.
Three main grades of gasoline are sold at retail gasoline refueling stations:
Some companies have different names for these grades of gasoline, such as unleaded, super, or super premium, but they all indicate the octane rating, which reflects the anti-knock properties of gasoline. Higher octane ratings result in higher prices.
Before 1996, lead was added to gasoline as a lubricant to reduce wear on engine valves. Leaded gasoline was completely phased out of the U.S. fuel system by 1996. Manufacturers recommend the grade of gasoline for use in each model of a vehicle.