To find out what octane your engine needs, check your owner's manual for the recommended octane level. Purchase the lowest octane gasoline your car can use without knocking. Higher octane gas costs more and consumes more energy to produce at the refinery. The following information may answer some of your questions about octane.
Octane ratings are a measure of the gasoline's ability to resist engine knock.
Octane ratings, by law, must be posted on each gasoline pump with a bright yellow sticker. On dispensers for alternative liquid automotive fuels, you will see different ratings that must be posted with a bright orange sticker. To determine which octane gasoline suits your car, check your owner's manual. If you're using the recommended octane and your car's engine is not knocking, you still may want to test whether you are buying gasoline with an octane rating higher than necessary. Try using a slightly lower octane gasoline.