ORLANDO (CBS) – Think you’re doing your car a favor by opting for premium gas? A new study from AAA says you’re better off saving your money.

“When it comes to gasoline, ‘premium’ does not mean ‘better’ if your vehicle doesn’t require it,” AAA’s John Nielsen said.

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About 70 percent of U.S. drivers have vehicles that require regular gasoline. And yet, in the past year, 16.5 million drivers have unnecessarily used premium gas more than 270 million times, according to AAA.

That all adds up to $2.1 billion spent last year on gas your car doesn’t need.

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AAA tests have shown that there’s no benefit to putting premium gasoline in a car that requires regular-grade fuel.

“Drivers see the ‘premium’ name at the pump and may assume the fuel is better for their vehicle,” Nielsen said. “AAA cautions drivers that premium gasoline is higher octane, not higher quality.”

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AAA recommends that drivers follow the recommendation in their owner’s manual when filling up.