Fuel Octane: Choosing the Right Gasoline What is octane rating? Octane rating is the measure of a fuel's ability to resist knocking, caused by the air and fuel mixture released prematurely in the engine, during combustion.   What fuel should I use in my vehicle? Check your owner's manual for the octane rating required for your vehicle by the manufacturer. You should choose that fuel when at the gas pump. Most gasoline vehicles run on…