Get to know the facts about gasoline octane.

What is octane? How will I know if I’m using the Is all premium or regular gasoline right octane level? equal? Octane is a measure of a gasoline’s antiknock performance – it’s ability to Listen to your car’s engine. If it doesn’t knock The octane rating for gasoline labeled as resist knocking, which is a metallic when you use the recommended octane, then “premium” or “regular” is not consistent across rattling or pinging sound that results from you are using the correct grade of gasoline. If the country. To ensure you know what rating uncontrolled combustion in the engine’s your engine runs well and does not knock or you are buying, look at the yellow octane sticker cylinders. ping when using a lower octane gasoline, there on the gas pump instead of relying on the name. will be no advantage in switching to a higher Why is octane important? octane. How much will it cost me to use a higher grade of gasoline? It may prevent engine damage. If a If your engine does knock, it doesn’t necessarily mean that something is wrong with gasoline is used with too low of an octane On average, it costs 5 cents per octane point rating than is required by an engine, then the gasoline. It may be a problem with the car’s ignition timing or exhaust re-circulation. between regular 87 gasoline and mid-grade 89 engine knock may result. Heavy and octane. It costs about 3 cents per octane point prolonged knocking or pinging may cause between mid-grade 89 and premium 92 octane power loss and may damage the engine. Should I ever switch to a higher gasoline. If you are consistently purchasing a octane gasoline? higher octane than you need, this money will How is octane rating add up quickly. determined? Sometimes engines may knock or ping, even when using the recommended grade of What else influences my car’s octane Gasoline is subjected to two testing gasoline. When this occurs, try using the next requirements? methods to establish its octane rating. The higher octane for a few fill-ups. Typically the knocking will stop. However, if the knocking motor method, runs the gasoline through Temperature: Hotter air and engine coolant an engine under load. The research or pinging continues, your vehicle may need a tune-up or other repair. increase your octane requirements. method, runs the gasoline in a free Altitude: Higher altitudes decrease your octane running engine. The octane rating you see Will my vehicle run better on high requirement. displayed on the pump is an average Humidity: Drier air increases your octane rating of the two methods. octane gasoline? requirement. Engine spark timing: If your engine’s spark How do I know what octane to No, not necessarily. Using a higher octane than timing is increased, your octane requirement use for my vehicle? is recommended will provide no additional increases. benefit to the engine. You may find that your Driving method: Rapid acceleration and heavy Check you owner’s manual. Regular gas mileage or power increases. In which case, loading increase your octane requirement. octane is recommended for most cars. you may get the same result from a tune-up. However, some cars with high compression engines, like sports cars, Some newer vehicles have electronic knock older cars, and certain luxury cars, may sensors, which may cause you to notice a slight For More Information: need mid-grade or premium gasoline. improvement in performance when using a 503-986-4670 higher octane gasoline. Visit our website at www.oregon.gov/ODA/MSD The facts on high What if I think a station is selling octane gasoline. lower octane gasoline than is Know the advertised? Do you buy high octane gasoline Who should I contact? facts… for your car because you want to Contact the Measurement Standards improve its performance? If so, Division at the phone number below. you should note: the Or, fill out a complaint form online at recommended gasoline for most www.oregon.gov/ODA/MSD. About gasoline octane cars is regular octane. In most cases, using gasoline with a higher octane than is recommend for your vehicle offers absolutely no benefits.

For a small percentage of vehicles, the engine knocks when using the recommended octane. In these rare cases, it may help to use a higher octane. Sometimes in these cases, however, the vehicle simply needs a tune-up. Measurement Standards Division Oregon Department of Agriculture Do not spend unnecessary 635 Capitol Street NE money purchasing higher than Salem, OR 97301-2532 recommended octane gasoline for Brought to you by: your vehicle. In this brochure you Phone: 503-986-4670 will find valuable information Fax: 503-986-4784 The Measurement explaining what octane is and TTY: 503-986-4762 how to ensure you are purchasing www.oregon.gov/ODA/MSD Standards Division of the the correct grade of gasoline. Oregon Department of Agriculture Revised 8/04