The Importance of Choosing the Right Octane Fuel for Your Vehicle

octanefuelFor the day-to-day rigors and routine operations of your vehicle, few things are as important as choosing the proper grade of octane for the unleaded fuel you put in your gas tank. Although the prices at the pump may make many consumers balk at choosing a high-grade, more-expensive octane, the truth of the matter is having the proper octane in your gas tank can actually improve vehicle performance.

First, let’s start with explaining what an “octane rating” is and how it’s determined. According to Mac Allen of, “the amount of additives in the fuel determines its octane rating. The octane rating is a measure of the gasoline’s ability to resist engine knock. This is the pinging or rattling sound that is the result of premature ignition of the compressed fuel and air mixture found in one or more cylinders. Fuel octane is typically rated at regular, 87 octane, mid-grade, 89 octane, or premium, 91-93 octanes. Most gas stations will offer all three grades of octane.”

How do you determine what the proper octane is for your car? The best place to look is in the owner’s manual of your vehicle. Auto manufacturers determine the proper compression levels needed for the fuel/air mixture to combust when the spark plugs fire. For most vehicles, the recommended level of octane is 87, but some models with turbo-charged or higher-compression engines require 89, 91 or 93.

Most newer-model vehicles contain engines with computer-controlled or variable valve timing and sensors that monitor engine knock. For these advanced engines, higher octane fuels (some with booster additives) will often be required to maintain engine power and performance. However, for older-model vehicles without computer-controlled timing or variable valve timing, there may be little to no point in using a higher-than-recommended octane fuel with stock timing settings. So, for older-model vehicles, using the lowest octane your vehicle can support will not harm the engine performance and will only save you money at the pump.

It is important to note that using an octane fuel that is too high for your vehicle will adversely affect its fuel efficiency. Higher octane fuel requires more heat and more precision to ignite correctly. For example, if a car is designed to use 87 octane, burning 93 octane can cause the engine to produce less power, thus making it require more fuel to perform at the same level. So you will want to be prudent and use the lower octane.

The fuel that you put into your vehicle is important, so we recommend that you always follow the guidelines set by the manufacturer. For more information on fuel octane and other information about gasoline, visit Exxon’s FAQ page.

As always, we would love to hear your feedback on fuel octane and on your experiences with engine knock. Leave us a comment below!