Why you probably shouldn’t be putting premium gas in your economy car

If you’re the kind of person who likes to pamper your economy car with premium gas, you may want to reconsider.

That “premium” label simply refers to the octane of the fuel. Higher octane fuel can lead to a performance boost, but only if the engine was designed for it. So if your car manufacturer doesn’t recommend using higher octane gas, then you’re probably wasting your money.

That was the conclusion, anyway, of a new study released Tuesday by the Automobile Club of Southern California. The auto club compared 87-octane, or regular gas, with 91-octane and 93-octane gas and found no measurable difference in either performance or emissions.

This isn’t exactly news. Companies involved in the manufacture and distribution of gasoline are pretty open about what octane is and how it affects vehicle performance.

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The real news is just how much money we’re collectively wasting because of this belief that premium gas is some kind of performance-enhancing drug for our cars.

In its study, AAA surveyed drivers and estimated that in the past year, 16.5 million Americans bought premium gasoline even though the owner’s manual for their vehicle calls for regular.

In total, AAA found Americans wasted more than $2.1 billion on premium gas their vehicles weren’t even designed to use.

Premium doesn't always mean better performance 

To conduct its test, AAA took several different vehicles designed for regular gas and ran them with the higher octane fuels on a dynamometer — basically a treadmill for cars. The club looked specifically at vehicle performance, fuel economy and emissions, and found no increase in any of these categories.

“If your owner’s manual recommends that you use regular fuel for your vehicle, you should just go ahead and purchase regular fuel,” said Megan McKernan, manager of automotive engineering for AAA in Southern California. “There’s no need to spend the extra money, because you will not see a benefit by using premium.”

Burkett Oil Company, a fuel supplier in the Atlanta area, is pretty clear on that subject:

The company pointed to the following video summarizing their findings:

Video

Even if a vehicle is designed to take advantage of higher octane fuels, the relative boost in performance can vary greatly by make and model. 

McKernan told KPCC that only a fifth of the cars on the road, often luxury vehicles, require high octane gas. That means the vast majority of us are driving cars or trucks that simply don’t need to be “pampered.”

So why are we doing it?

“Part of it is just in the name itself, because of the term ‘premium,’ and it’s the most expensive one you see at the gas station, so there’s kind of that inherent assumption that it’s better,” McKernan said.

The lesson here is that if your vehicle was designed for premium, you should buy premium, though McKernan couldn't say what would happen in the reverse case — using lower octane fuel in a car that needs premium fuel.

“One of the main questions actually that we’ve received since releasing the study is, ‘Well, what about the reverse? And what happens if you use regular gasoline in a vehicle that actually requires premium?’ So that’s something that we’re considering looking into,” she said.

The only factor McKernan said AAA could prove made a difference was the quality of fuel additives. She cited the Top Tier program, which certifies fuels that use high quality detergents to prevent buildup on engine parts.

But most, if not all, major brands, including ARCO, 76, Chevron, BP, Shell and Exxon, use these “Top Tier” detergent gasolines. For Chevron and several other brands, that additive is called “Techron.” You can see the full list of Top Tier gasolines here.

You can read the full AAA report here:

Document: Premium costs