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Is Premium Gas Needed In Regular Cars?

By Aaron Crowe

Saving about $5 by filling up your car with regular gas instead of premium isn’t much of a savings, but over the lifetime of a car it adds up.

No matter how much money you save, is that savings worth it if the car’s manufacturer recommends using premium gas? And on the flip side of that question, is it worth paying more for premium gas for a car that will run just as well on regular, low-octane gas?

The answers depend on what kind of car you drive, if it will have engine trouble with a lower grade gas, and if you mind getting lower performance (such as gas mileage) by using regular gas.

Scott Golembiewski, a Washington state entrepreneur who has worked with turbocharged vehicles that require premium gas, says he’s heard of drivers of cars requiring premium gas mixing a quarter of a tank of regular gas with premium gas and not having engine problems. But it’s a risk.

“When you own a vehicle and you want to take good care of it, do you really want to risk things?” Golembiewski asks.

Sports and luxury cars, and turbocharged cars, often require premium gas with high octane levels of 91 or higher to keep fuel burn in control and avoid engine knocking. That’s the sound when an engine’s piston is only partially through the compression stroke, which can physically break the piston in severe cases.

Premium gas has additives that suppress the knocking and allows the engine to run at high compression ratios for more horsepower without knocking or damaging itself, says Mike Arman, who has also worked on high-performance cars. Having high compression ratios is the cheapest, easiest way for a designer to get more horsepower out of an engine, Arman says.

Most modern vehicles have knock sensors that will adjust the engine’s timing for lower octane gas, though performance will be sacrificed, says Alex Gutierrez, senior market analyst for Kelley Blue Book. “If done frequently, using lower than recommended octane fuel can damage the engine,” Gutierrez says.

Running a high compression engine on regular gas will damage older engines, says Arman.

“While the newer engines won’t be damaged, they will not make rated power and their fuel mileage may suffer,” Arman wrote in an email.

He recommends doing what the owner’s manual suggests and using premium gas when recommended, especially if you drive fast or your car or truck is pulling a heavy load such as towing a trailer or boat.

While newer vehicles that manufacturers say should be using premium gas can probably get away with using regular gas, the recommendation is a safety measure that will help the car run better and can help the manufacturer have fewer claims on its warranties, Golembiewski says.

“They’re going to recommend something that’s going to protect them,” he says.

But beyond the turbocharged Porsches and other luxury cars that you’d expect to need premium gas, there are plenty of “regular” cars that also need premium gas, according to a story by Cars.com.

Among them are the 2013 Chevrolet Volt, a hybrid electric car that the owner’s manual says should be run on premium gas of 91 octane or higher, or “you could damage the engine.”

The owner’s manual for the 2013 Smart ForTwo, which has a MSRP of $12,490, calls for premium gas, partly to increase mileage approximately 3 mpg better than regular fuel.

That’s not much of a mileage improvement for the 33 cent per gallon national average price difference between regular and premium gas, according to the AAA Fuel Gauge Report. For standard cars, Scientific American found that premium gas didn’t deliver added benefits.

As the owner of two high performance Mercedes cars, Mitch Goldstone, the president of a photo scanning website, says he has never had an issue using regular gas, despite the car maker recommending using premium gas. Goldstone, who lives in Irvine, CA, says he has always used regular gas to save money, and has always gotten the same gas mileage from his cars.

Another Mercedes owner, Marissa Vallbona of San Diego, says she has been filling it with mid-grade gas for the past five years and has never had a problem. She has her car serviced at the dealership and has been told it’s in excellent condition.

“One day I was filling my tank with premium gas when a mechanic told me that there is little difference between mid-grade and premium gas,” Vallbona wrote in an email. “but there is a price difference in my favor if I switch to mid-grade gas.”

“He assured me that there was zero difference in the car’s performance,” she wrote. “He did say that if I used regular gas, there would be problems and that I should stick to mid-grade.”

For drivers who put premium gas in their cars when the manufacturer says that regular gas is fine, don’t waste your money. The higher octane gas won’t provide an extra boost in gas mileage or increase acceleration.

“If a vehicle only requires 87 (octane), you can expect to see little to no performance boost,” says Gutierrez. “So consumers might as well save their money and stick to the cheapest gasoline their vehicle can handle.”

Aaron Crowe is a writer in the Bay Area who specializes in personal finance topics for CheapCarInsurance.net.