Octane numbers mean and how they impact your car

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87, 89, 91 – 93. To many people, this just seems like a series of numbers. However, to those who fill the tanks of their cars constantly, these numbers have become very familiar. Car owners still wonder to this day what exactly these numbers mean, and why there are different types of gasoline for different types of vehicles. Lucky for you, this is the perfect place to clear up all the confusion behind these four numbers, known as different octanes.


Octane is how much compression the fuel can withstand before combusting. This rating is a measure of the fuel’s ability to avoid knock. Knock occurs when the fuel is prematurely ignited in the engine’s cylinder, which degrades efficiency and can cause damage to the engine. Most gas stations offer 3 octane grades, 87 (regular), 89 (mid-grade) and 91-93 (premium). The higher the octane number, the more resistant the gasoline mixture is to knock.

The use of higher-octane fuels also enables higher compression ratios, turbocharging, and downsizing/down speeding, which all contribute to engine performance. The higher-octane numbers also contribute to higher prices. Now, you as a customer may wonder why you’re paying more for higher octanes if your vehicle could function just fine on lower octanes. Read on to find out why!

  • 87: regular gasoline that works best for most vehicles. This octane of gas tends to cost 15-20 cents less than premium, ranging from $1.80 – $2.50 gallon. Myths have circulated that stated higher octane gas gives your vehicle many benefits, including better mileage, faster top speeds or better performance overall. However, these are just myths, and in fact, there is no need to fill your tank with any octane higher than 87 unless specifically instructed to. The only reason you may have to switch over to a higher octane is if your engine knocks when you use the recommended fuel.


  • 89: mid-grade gasoline that is a mix of premium and regular gas (first appeared in 1995). Medium octane gas usually is around $2.50 per gallon. This octane of gas can be used in vehicles of all sorts. If your car’s engine starts to knock while using regular grade gas, it’s wise to consider upgrading to mid-grade gasoline. It’s main purpose is so that car owners have another option besides regular fuel that is not quite as expensive as premium.


  • 91-93: premium gasoline that is used in luxury and sports cars. All of the super cars that are out on the streets use 91-93 octane gas. This is due to the fact that engines with high compression ratios or turbochargers often require high octane fuel found in premium gas for optimal performance and fuel efficiency. The average premium gas price hovers at around $2.80 per gallon. The higher octane enables premium gas with greater resistance to early ignition, which preserves the state of the engine. It also causes less knocking. But all the benefits come with a price.


Even with the right gasoline if you still experience knocking, we strongly recommend getting your checked. As it might be time for you to replace the spark plug.

A professional will be able to determine the right cause and ensure your car gets the care it needs.