Octane showdown: The myths of premium vs. regular gas

One of the questions we often hear from our clients is, “Should I use premium gas?” And at $3 per gallon for regular gasoline, who wants to tack on 15 cents to 30 cents extra without good reason? The good news is that—in most cases—you do not have to use premium gas.

But there’s a lot of misunderstanding with octane ratings (in part because of slick advertising campaigns), and we’re going to clear those up for you. Depending on the vehicle you drive, you’ll either save money or learn how to prevent damage to your engine.

Let’s start by explaining “octane.” When you press the “87,” “89,” or “93″ button at the gas station, you’re choosing the gas based on its octane. This indicates a gasoline’s ability to resist engine knock or pinging, which occurs when the spark plug ignites the air-fuel mixture in the engine cylinder before it’s supposed to.

The resulting effect: While the piston is still moving upward to compress the air-fuel mixture, the force from the premature explosion pushes down on it and wreaks a little havoc. But the higher the octane rating, the longer the gas takes to ignite. The longer the gas takes to ignite, the less the chance of premature ignition.

And that is the key difference between regular and higher octane fuel. Premium gasses are no cleaner than any other. They don’t boost your fuel economy. They’re simply designed to ignite more slowly.

What does that mean to you? You should only choose premium fuel for two reasons: Your engine knocks or pings without it, or your vehicle manufacturer requires it. Notice that we didn’t say recommend. There is a difference.

Some high-performance engines require high-octane fuel to prevent engine knock and pinging. If you own one of these vehicles, don’t be tempted by the lower price on 87 octane. It will cost you dearly in the long-run because prolonged use of 87-octane fuel in these engines can lead to serious engine damage.

At the same time, the superior reputation of premium fuel comes in large part from successful marketing campaigns and from the fact that premium automotive brands like Acura, BMW and Lexus recommend them for many of their vehicles. They do so because it helps to distinguish their high-end cars from other vehicles and because they want owners to get out every bit of performance they’ve engineered into the vehicles. When you use regular gas, you lose some of that performance—about 5 horsepower (hp), according
to automotive engineers. Instead of getting all 280 hp, you might only be getting 275. Most of the time, though, you won’t even notice the difference.

If you drive a car that is designed for 87 octane fuel, using premium gas can actually cause problems. It can detune the engine, and because it ignites slower, premium gas can make it difficult to start a vehicle in extremely cold weather.

Keep in mind that automobiles are built for use around the world—often in areas where premium gas isn’t available. Automobile manufacturers know this and need their vehicles to perform well in those markets, too.

If you’re still not sold on the idea of saving yourself some money and sticking to regular, consider this consumer notice from the Federal Trade Commission (FTC). The FTC stated: “(I)n 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.”

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