Reader asks about octane rating

Most vehicles are designed to operate normally using 87 octane fuel unless the owner s manual states that midgrade (89) or premium (91+) is required. Photo by James Halderman

Most vehicles are designed to operate normally using 87 octane fuel unless the owner s manual states that midgrade (89) or premium (91+) is required. Photo by James Halderman
Cars
By James Halderman
Updated Nov 25, 2016
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Wheels: An e-mail from Bob says, “I’ve been looking at new cars and some specify that the engines can use 87 octane, whereas some others recommend midgrade (89 octane) or premium (91+). I want to use regular gas (87) in the car I purchase. I’m a confused new car shopper.”

Halderman: Good question! Some automotive manufacturers, such as Ford for my Mustang, “recommend” the use of premium (91+ octane) for “best performance” and to achieve the full rated horsepower (412) that the engine can deliver. However, if regular is used, the performance is reduced and the horsepower rating is reduced to “just” 402 horsepower.

When I use regular, I do not notice a drop in power, but I do notice a drop in fuel economy. There is a difference between “recommended” and “required.” As long as the owner’s manual states that premium is recommended (not required), then regular grade (87 octane) can safely be used. However, if the owner’s manual specifies that only premium should be used, then using regular grade gasoline may cause engine damage. Best wishes in selecting a new vehicle and enjoy driving it.

Have an automotive related question? Write to Jim at jim@jameshalderman.com.

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About the Author

James Halderman