Skip the auto shop - Our mechanics make house calls
  1. Home
  2. Articles
  3. Which Type (Octane) of Gas Is Recommended for My Car?

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

P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...

Related questions

Q: Gas gauge malfunctioning and Service Engine Light on

Thank you for asking about your 2006 GMC Sierra 1500 HD. More than likely, the problem is the fuel sensor, which is built into the fuel sending unit. This assembly is mounted in the gas tank. This is a common...

Q: Fuel promblem

You may have excessive dirt inside the tank that has clogged the fuel filter to the point that the dirt has gotten into the injectors, causing the misfire. Remove the fuel filter and blow through it to see...

Q: Does Gas Go Bad?

Gasoline, like milk, goes bad over time. Gasoline is usually good for about 6 weeks before it starts to turn into a varnish-like substance. This varnish-y fuel is sticky and makes all of your fuel system components non-operational. If...