Premium gas comes with a premium price tag, but many drivers feel it's a fair cost to pay for gas that’s supposedly higher in quality. Now, new research from AAA suggests that shelling out extra money at the gas pump produces zero benefits in most cars. As CNN Money reports, 16.5 million Americans spent money in the past year on premium gas their cars didn’t need, adding up to over $2 billion wasted.

Before splurging on a tank full of premium gas, check your car’s owner’s manual to see what type of fuel is recommended. The vast majority of vehicles in America—about 70 percent—are built to process regular fuel. When premium gas is added instead, AAA found that these cars showed no significant improvement in performance, fuel economy, or emissions.

When drivers see the word “premium,” they might mistakenly assume it means higher gas quality. What the label actually refers to is the gas’s octane rating. High octane gas is better equipped to handle high pressure conditions inside an engine. Because most car engines never reach such high pressures, they’re no better off with the higher-priced gasoline.

If you’re part of the 16 percent of Americans who own a vehicle that does require premium fuel to run, filling up with anything less can cause engine damage. There’s also a fraction of cars that fall in a middle ground where premium gas is suggested by not necessarily required. Even in these cases drivers should be able to get away with regular as long as engine knocking caused by pre-ignition doesn’t become an issue (knock sensors and engine management systems in most modern cars already take care of this).

[h/t CNN Money]

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