LOS ANGELES (CBSLA.com) — American motorists have wasted more than $2.1 billion by spending extra money on premium gasoline for vehicles that are equipped to run on regular fuel, according to a AAA study released Tuesday.

In the past year, 16.5 million drivers needlessly used premium-grade gasoline in their vehicle at last once a month, according to the study.

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The Automobile Club of Southern California reports there is no benefit to using premium gasoline in a vehicle that requires regular fuel.

“Premium gasoline is specifically formulated to be compatible with specific types of engine designs and most vehicles cannot take advantage of higher octane rating,” said Megan McKernan, manager of the Automobile Club of Southern California’s Automotive Research Center.

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The Auto Club tested a variety of vehicles with different types of engines and compared their performance when fueled with regular and premium gasoline.

The vehicles were tested on horsepower, fuel economy and tailpipe emissions.

According to the study, 70 percent of U.S. drivers own vehicles that require regular gasoline, 16 percent have vehicles that require premium fuel, and 14 percent require mid-grade gas or use alternative energy.

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