Why You Might Not Actually Need Premium Gas

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

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

Some cars require premium gas, but others simply carry a recommendation that owners use it. We wanted to see whether owners can save money by using regular gas in those cars that merely recommend premium fuel use.

Testing at the Consumer Reports Track

To determine whether using regular gas in a vehicle that recommends premium gas had any effect on fuel economy or acceleration, we evaluated two models: a 2015 Acura TLX four-cylinder and a 2016 Nissan Maxima V6 (both shown below). Each recommends but does not require the use of premium gas. That guidance can be found on the inside of their fuel-filler door and is often explained in greater detail in the owner’s manual.

As long as owners fuel the vehicle in accordance with the instructions from the owner’s manual, they should be protected by the powertrain warranty.

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

All the tests were conducted following our stringent fuel-economy protocol, with consumption measured using an inline fuel meter.

Both sedans achieved the same fuel economy when tested with regular fuel as they did 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 drivers might notice a decrease in performance when running on regular gas, but our test results said otherwise. The 0-60 mph acceleration times were identical in the TLX and Maxima on regular and premium gas.

We contacted Acura and Nissan, asking why they recommend using 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 added that there could be some conditions where performance—which includes fuel economy—might be compromised, such as on extremely hot days. Nissan also said that it recommends the use of premium fuel to guarantee advertised performance.

Money in Your Pocket

Gas prices have been on the rise lately, with the national average now about 44 cents higher per gallon than at the same time last year. Right now, there is a significant cost difference between regular and premium gas of 52 cents, according to AAA's fuelgaugereport. Owners who pay for premium when they don't need it can find a real dent in their budget.

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

What's the Downside?

It’s okay to use regular even if the manufacturer recommends using premium gas. But owners should check their 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, a connection was never made between using premium fuel and reliability. The manufacturers talk about higher octane only in terms of a car’s performance.

What’s more, in the Acura owner’s manual the automaker 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 owners make the switch and think their car is performing sluggishly, or they hear knocking or pinging, they should go back to premium fuel.

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

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