September 20, 2016 8:31 AM EDT

U.S. drivers wasted more than $2.1 billion dollars in the last year by filling regular vehicles with pricier premium-grade gasoline, despite there being no tangible benefit to doing so.

The AAA researchers who carried out the study came to this conclusion after testing 87-octane (regular) and 93-octane (premium) gasoline in vehicles, then evaluating them for their performance, fuel economy and emissions.

The test results found no significant increases in any tested category, which indicates that there is no advantage to using premium gasoline in a vehicle that only requires regular-grade fuel.

AAA found that 16.5 million U.S. drivers unnecessarily used premium-grade gasoline in their vehicle at least once over the past year. In the same timeframe, they discovered that U.S. drivers unnecessarily used premium gasoline in their vehicle more than 270 million times.

“Drivers see the ‘premium’ name at the pump and may assume the fuel is better for their vehicle,” said John Nielsen, AAA’s managing director of Automotive Engineering and Repair. He urged drivers to follow the owner’s manual recommendations for their vehicle’s fuel in the future.

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