Drivers who put premium gas in vehicles that only need regular are wasting billions of dollars, according to an AAA test.
The auto club released the results of a test and survey on Tuesday.
It said that drivers burn more than $2.1 billion annually pumping premium when it adds no benefit to their particular vehicles.
"AAA cautions drivers that premium gasoline is higher octane, not higher quality, and urges drivers to follow the owner's manual recommendations for their vehicle's fuel," said John Nielsen, AAA's managing director of automotive engineering and repair.
AAA said it conducted a fuel evaluation to determine the benefits of using premium in cars that only require regular gas. The evaluation included 16.5 million Americans over the past 12 months.
It used industry-standard test protocols to test vehicle performance, fuel economy and emissions.
As a result, AAA said it found no added benefit to using premium gas, but only if the vehicle requires regular fuel-grade.
It said 70 percent of U.S. drivers currently own a vehicle that requires regular gas. Only 16 percent of drivers use vehicles that require premium fuel.
The remaining 14 percent own a vehicle that requires mid-grade or an alternative energy source.
Over the past year, AAA said 16.5 million drivers unnecessarily used premium-grade gas at least once.
During the same time period, drivers unnecessarily used premium gas in their vehicles more than 270 million times.
"This is the second consumer friendly tip AAA researchers have given motorists about gasoline in the past few months," said Amy Parmenter, AAA spokesperson. "First they learned that top tier gas is the best quality gas for all cars and now they know there's no need to fill 'er up with premium, unless the manufacturer says so."
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