Skip the auto shop - Our mechanics make house calls

Which Type (Octane) of Gas Is Recommended for My Car?

octane

When someone pulls up to a gas station, the first thing they’ll see is the big sign lit up with the prices for the different grades of gasoline. There’s regular, premium, super, and a number of other variations of names for these grades. But which grade is the best?

The meaning of octane

Most people think that an octane rating is to gasoline what a "proof" number is to alcohol. This is a common misconception, and the real source of the octane rating is a bit more unexpected. Octane is actually a measure of how resistant that grade of gasoline is to engine knocks at higher compression in the combustion chamber. Less stable fuel, below 90 octane, is fine for most engines. In high-performance engines though, the high compression of the air/fuel mixture may be enough to ignite the mixture before the spark plug supplies the spark. This is called a "ping" or "knock." High octane fuel is able to resist the heat and pressure of high-performance engines and avoid knocking, igniting only when the spark plug sparks.

For cars driven normally, engine knocks are easier to avoid and the higher octane does nothing to improve performance. In the past, cars would need higher octane fuel every few years due to deposits in the engine increasing compression. Now, there are cleaning detergents and chemicals in all major brands of gas that prevent this build-up. There is no reason to use a higher octane of fuel if the engine does not knock or ping.

How to identify what octane your car needs:

  • First, open the fuel filler door.

  • Next, look at the gas cap and the inside of the fuel filler door. One of these should have the recommended octane fuel for the vehicle written on it.

  • The typical way the recommended fuel octane is listed is as follows:

    • XX Octane (sometimes “AKL” is put in place of octane) recommended
    • XX Octane minimum
  • Using a fuel with an octane rating under the minimum requirement is likely to cause engine knocking.

  • Choose fuel based on the octane number, not the name (regular, premium, etc.) of the grade.

  • If the cap is yellow, then the vehicle is a flex-fuel vehicle that can take E85 ethanol.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

P0121 OBD-II Trouble Code: TPS "A" Circuit Range Performance Problem
P0121 code definition Throttle Pedal Position Sensor/Switch (TPS) A Circuit Range Performance Problem What the P0121 code means P0121 is a generic OBD-II code which indicates that the Engine Control...
Insurance Requirements for Car Registration in Kentucky
The Kentucky Transportation Cabinet requires that all drivers in Kentucky carry liability automotive insurance, or “financial responsibility” in order to operate a vehicle legally and maintain vehicle...
The Traveler’s Guide to Driving in Malaysia
CraigBurrows / Shutterstock.com Malaysia is a popular destination for many tourists today. The country has amazing sights and attractions that you will want to explore....


Related questions

Q: After fuel pump replacment, car uses more gasoline

There is always a chance of something going wrong with a repair, but let's not start there. There may be a new concern, such as a vacuum leak or a sensor causing false readings. Since there was a recent repair,...

Q: Vehicle not starting after part replacement.

Hi, If you had all this work done to the engine and now when all is said and done, the engine will not start then I would say that something was not hooked up or not put together correctly. Your...

Q: Gas leak

There are several lines and hoses that run underneath your vehicle that carry fuel. It is possible that due to the age of your vehicle that a line has rusted through or deteriorated enough to allow fuel to leak. I...