High Octane Fuel Truths for Car Owners

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Do higher-octane fuels deliver better performance and are worth the extra cost? Find out now with the lessons learned from a practical test comparing 87, 91, and 93-octane for fuel efficiency and horsepower.

The Burning High Octane Fuel Question

It’s easy to place faith in the mistaken belief that if anything is considered higher quality and costs more, then it must be better for your car. Especially when it comes to affecting your vehicle’s performance. But is this always true?

Earlier, we’ve reported that according to the American Automobile Association (AAA), Americans are six times more likely to choose a gas station based on gasoline price rather than quality. But what if you are more concerned with performance over cost?

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Well, that can depend on how you view “performance.” Are we talking about feeling like you are getting a little more zip with acceleration from high octane fuel bought at the pump? Or are we talking about performance based on choosing the fuel that is actually rated best for your particular car to run optimally and cut down on maintenance and repair costs down the road?

About Octane Ratings

Fuel ratings you will find at the pump typically come in three octane grades: regular (usually 87 octane), mid-grade (usually 89 octane) and premium (usually 92 or 93). The octane rating is a measure of the fuel’s ability to resist combustion. The higher the rating, the less likely the fuel-air mixture will combust too early during the compression stroke as pressure and heat build within the cylinder in a 4-cycle engine.

If the fuel combusts too soon in the cycle (i.e., when the piston is in the wrong position of its stroke within its cylinder) your engine will experience a knocking, rattling or pinging sound as a result and will adversely affect how your engine operates.

What this comes down to is that depending on the physical design (and computer control) of the engine, vehicles are typically designed to perform optimally with a specific octane-rated fuel. If you put the wrong octane-rated fuel in a modern car you might not notice any difference in operation because the computer will adjust for it. If you put the wrong octane-rated fuel into an older model car, you are more likely to experience that knocking sound. In either case, using higher priced higher-octane gas is needlessly wasting money with no advantage gained in performance of any kind in the average car.

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In fact, according to the Federal Trade Commission publication FTC Facts for Consumers: The Low-Down on High-Octane Gas:

“Regular octane is recommended for most cars. However, some cars with high compression engines, like sports cars and certain luxury cars, need mid-grade or premium gasoline to prevent knock...the recommended gasoline for most cars is regular octane. In fact, in most cases, using a higher-octane gasoline than your owner’s manual recommends offers absolutely no benefit. It won’t make your car perform better, go faster, get better mileage, or run cleaner. Your best bet: listen to your owner’s manual.”

In other words, stick to what your owner’s manual says when it comes to the gas you put in your particular model of car.

Performance and Fuel Efficiency Tested

In a recent Project Farm YouTube channel episode, the host puts higher octane fuel (with and without ethanol) to the test in terms of performance (the amount of pull and speed achieved) using a small engine garden tractor and fuel efficiency (how long each fuel lasts) using a Honda generator under a specific load.

Basically, the message is that from his small engine tests, buying higher-priced higher-octane fuel will not really provide any advantage in the engine’s performance. The only exception to this is if you were to alter the timing of the engine to optimize the conditions of the fuel-air mixture so that the most compression is achieved with each compression, ignition, and power stroke made during the 4-cycle operation. But outside of racing applications, most car owners will not (and should not) do this.

That said, here are the octane comparison results using small gas engines:

And finally…

For additional articles related to cars and fuel, here are a few selected articles for your consideration and enjoyment:

Timothy Boyer is Torque News automotive reporter based in Cincinnati. Experienced with early car restorations, he regularly restores older vehicles with engine modifications for improved performance. Follow Tim on Twitter at @TimBoyerWrites for new and used vehicle news.

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