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

P0222 OBD-II Trouble Code: Throttle/Pedal Position Switch/Sensor B Circuit Low Input
P0222 code definition Throttle/Pedal Position Switch/Sensor B Circuit Low Input What the P0222...
How to Buy Fuel Treatments
Adding a fuel additive to your gas tank when you fill up is one way to clean vital engine parts of deposits, improve the performance of your engine,...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...


Related questions

Q: Engine stalled, made clicking noise, made smoke

Hi there, thanks for writing in about your 2011 Mercedes E550. This sounds like potentially a bad crankshaft sensor. I would recommend having the car scanned to see which trouble codes show up.  More than likely, there will be more than...

Q: Why do I have a loud vibration?

Hello. You should verify whether the timing belt was put on correctly. All the pulleys have to be in the right position in order for the valves to open and close at the right time. If the belt is out...

Q: How do I change the optional message center display?

The optional message center display allows you to choose what information is displayed. These are the available options: fuel gauge, distance to empty, and bar tachometer; fuel gauge and round analog tachometer; fuel gauge, round analog tachometer, and engine coolant...