6 busted fuel-economy myths to save on gas

Replacing air filters improves mpg
Replacing air filters improves mpg © sima/

Myth: Replacing an air filter on a modern engine will improve your fuel economy.

It used to be that replacing an air filter would give your fuel economy a kick in the right direction, and if your vehicle has an old engine with a carburetor, it still will.

But according to, that's no longer the case with modern, fuel-injected engines. "The fuel-injected engine will deliver better fuel economy, lower emissions and, no matter how you measure it, better performance all the way around," Molla says.

Today's fuel-injected vehicle has an onboard computer that measures the mass of the air entering the engine and automatically adjusts the fuel flow accordingly, Molla says.

He says that's why something such as a dirty air filter won't have an appreciable effect on gas mileage. That doesn't mean you shouldn't replace your air filter.

According to a new study at Oak Ridge National Laboratory, replacing a clogged air filter on a fuel-injected, computer-controlled gas engine can improve acceleration time by approximately 6 percent to 11 percent.

How to save: Pay attention to the maintenance schedule in your owners manual. Some garages promote overly aggressive air-filter replacement schedules, which is an unnecessary cost, Boundy says. An air filter costs $10 to $15. If you add labor costs, it could boost the cost by $19 to $60, according to


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