Gasoline octane ratings: What do they mean?

April 4th, 2023 by

Gas prices have been on the rise all across the country over the last few years. They’ve leveled out a little in more recent months, but even still, they’re a whole lot higher than they used to be. This has some people thinking twice about the type of fuel they put into their cars, trucks, and SUVs. It also has them asking questions such as, “What is an octane rating?” and “What does an octane rating mean?”

If you buy fuel for your car, truck, or SUV on a regular basis, you’ll know which octane rating of gasoline to choose but, you’ll also need to know the difference between them. The team at Cochran Chevrolet Youngstown has put together this article to help you understand everything there is to know about octane ratings.

What Is an Octane Rating?

zoomed in picture of a gas pump focused on Unleaded fuel

When you pull up to a fuel pump, you’ll notice that it can dispense several different types of gasoline. You’ll usually have a regular option along with a midgrade and a premium option. Next to the names of each of these options, you’ll see a corresponding number. This number is the octane rating for the gasoline that you’ll be buying.

So, what is an octane rating? Well, a gasoline octane rating is essentially a measure of its fuel stability. The higher a type of fuel’s octane rating is, the more stable it’s thought to be. You’ll need to choose the right octane rating of gasoline for your specific car every time you fill it up with fuel at the pump.

What Does an Octane Rating Mean?

Now that you know what an octane rating is, let’s talk a little more about what an octane rating means. It can be confusing trying to figure it out when you’re standing in front of a fuel pump thinking about which octane rating you should choose.

As we mentioned above, there are typically three types of fuel available at most gas stations throughout the U.S., and they each have a different octane rating:

  • Regular has an octane rating of around 87.
  • Midgrade has an octane rating of 89 or 90.
  • Premium has an octane rating of 91 to 94.

The octane rating of gasoline represents the pressure that it will take for fuel to spontaneously combust within your engine. Fuels with higher octane ratings will be more stable and will require more pressure to combust. This will make them better options for some cars.

One thing we should add is that some gas stations have also started to add E85 to the mix. E85 is a gasoline alternative that is made up of 85% ethanol and 15% gasoline. And what is the octane rating of E85? It can actually be anywhere from 100 to 105, which makes E85 a high-performance fuel that will work well in vehicles that are equipped to run on it.

How Are Fuel Octane Ratings Measured?

If you were to look at the different types of fuel, you wouldn’t notice a big difference between them. This might cause you to wonder how fuel octane ratings are even measured. It can be a very complicated process, but the standard means of testing the octane rating of gasoline is with an octane testing engine. This engine relies on primary reference fuels to reveal the octane ratings for gasoline.

How Will the Octane Rating of Gasoline Impact Your Vehicle?

Today’s cars, trucks, and SUVs have engines that are designed to burn through fuel by utilizing a process called controlled combustion. When this process takes place, a flame will start off at the car’s spark plug and steadily burn throughout the engine’s cylinder until all of the fuel in it is burned.

If you put the wrong type of fuel in your car, though, this process won’t play out as expected. Instead, what is called spontaneous combustion can occur. This is when both the temperature and pressure in a cylinder build up to a point where unburned fuel will start to ignite and can cause what’s known as a “knock” in an engine. This could potentially lead to damage being done to the engine if you use fuel with the wrong octane rating all the time.

Which Octane Rating of Gasoline Should You Choose?

The good news is that you shouldn’t have to worry too much about which octane rating of gasoline to use when you fill up your vehicle with gas. Regular gas is going to work just fine for the vast majority of vehicles. It also just so happens to be the most affordable fuel option on the market.

But before you assume that you should put regular gas into your car, truck, or SUV, it would be well worth flipping through the owner’s manual for your vehicle. This should tell you which octane rating of gasoline you should be using. You’ll want to go by what your owner’s manual says to get the best results.

You might also want to speak directly with a trusted technician from the service center at a local auto dealership, such as Cochran Chevrolet Youngstown. They’ll provide you with some much-needed insight into which fuel octane ratings would be your best choice. You’ll also be able to ask them to explain in more detail about octane ratings.

Make Sure You Choose the Right Octane Rating for Gasoline

As we just alluded to, most vehicle owners will be able to get away with using regular gas in their cars, trucks, and SUVs. But after finding out the answer to the question, “What does an octane rating mean?”, you might want to do some digging through your owner’s manual to see which octane rating for gasoline would be best for you.

You might also want to ask the talented team from #1 Cochran more about octane ratings. We can explain them in more detail and tell you how the octane rating that you choose can affect your vehicle. Call us today to schedule service at our service center.


Gas Station Pump by Robert Geiger is licensed with CC BY 2.0

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