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Pumping gas
Images by Fabio—Getty Images

Premium gas sounds like it’s something special, but it actually translates into paying extra for a higher octane without a performance or fuel economy benefit for many cars.

That's what we found after running tests at our 327-acre track.

While some cars require premium gas, many others simply carry a recommendation to use it. We wanted to see whether you can save money by using regular gas in cars that merely carry the recommended premium fuel label.

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Testing at the Consumer Reports Track

To find out whether using regular gas in a vehicle that recommends premium gas had any effect on fuel economy or acceleration, we evaluated two models: the 2015 Acura TLX four-cylinder and the 2016 Nissan Maxima V6. Each recommends but does not require that the owner put in premium gas—guidance found on the placard on the backside of their fuel-filler door and often explained in greater detail within the owner’s manual.

So long as you fuel the vehicle in accordance with the manual, you are protected by the powertrain warranty.

In order to purge the cars of premium that could be in the fuel system, we drove them nearly dry, then ran through a full tank of regular gas before starting testing.

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All tests were conducted following our stringent fuel economy test protocol, with consumption measured through an inline fuel meter.

Both sedans achieved the same fuel economy when tested with regular fuel as with premium. During this testing, the cars felt and sounded the same; we did not experience any engine pinging or knocking noise in either car when using regular fuel.

The owner's manuals indicate that you might notice a decrease in performance when running on regular, but our test results say otherwise. The 0-60 mph acceleration times were identical in the TLX and Maxima on regular and premium gas.

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We contacted Acura and Nissan, asking both why they recommend premium gas.

An Acura spokesperson referred us to the TLX’s owner's manual, which states, “Use of lower octane gasoline can cause occasional metallic knocking noise in the engine and will result in decreased engine performance.”

A Nissan spokesperson wrote in an email that "it is possible for the same performance to be realized using non-premium fuel." But the spokesperson did add that there could be some conditions where performance—which includes fuel economy—might be compromised, such as on extremely hot days. Nissan goes on to say that it is recommended to use premium fuel to guarantee advertised performance.

Money in Your Pocket

While gas prices remain historically low, the cost difference between regular and premium gas has increased over the past year. In 2015, there was a 39-cent difference between regular and premium, according to fuelgaugereport. But as of this writing, there is a 47-cent difference in the national average price of regular and premium gas. And given the lower pump prices overall, that 8 cents is an even greater percentage.

Below we highlight the potential savings using regular instead of premium fuel assuming 12,000 miles per year and current gas prices.

Fuel Economy Savings Per Year
30 mpg $188
25 mpg $226
20 mpg $282
15 mpg $376

What's the Downside?

So it's okay to use regular even if the manufacturer recommends using premium gas. But check your car owner’s manual before making the switch, and remember that some automakers say premium is required.

Wondering about the long-term effects of switching to regular fuel? Here's what we know: In conversations with manufacturers, never was there a connection made with using premium fuel for reliability reasons. The manufacturers only talk about higher octane in terms of performance.

What's more, in the Acura owner's manual, Acura only recommends using "top-tier detergent gasoline"—which can be of any octane grade, regular or premium—for performance and reliability reasons. But there is nothing in the manual that equates premium gas with improved reliability.

That said, if you make the switch and think your car is performing sluggishly, or you hear knocking or pinging, go back to premium fuel.

Beyond these test findings, it is key to note our car reliability data consistently show that the most dependable cars tend to be those running on regular fuel.

Consumer Reports has no relationship with any advertisers on this website. This article originally appeared in Consumer Reports.