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The numbers are small, and you probably won't feel the extra power. But they do work. F5 Bag Air Filters

If you've ever been to an auto parts store, you've probably seen air filter boxes that claim extra power and more torque over the factory filter. But being so cheap and easy to install, it's hard to believe these filters actually produce any observable gains. Well, Jason Fenske of Engineering Explained put these claims to the test, and it turns out that yes, high-performance air filters do actually yield more power. But not much.

Fenske put together a dyno test using his personal Subaru Crosstrek, comparing four different air filters: The dirty OEM item already the car, a new OEM filter, a cheaper aftermarket non-performance filter sold by CarQuest, and a high-flow performance filter made by K&N. He finds that on the dyno, the aftermarket filters do in fact make more than the OEM unit, with the most gains produced by the K&N filter (around four horsepower and five lb.-ft. of torque, or around 2.6 percent and 3.7 percent, respectively).

Fenske also tests out the filters in a real-world environment, testing acceleration times between the four candidates. Like on the dyno, he sees incremental increases, with the K&N filter coming out on top. It produced a 2-3 percent improvement in acceleration time versus the stock unit.

What Fenske doesn't test is just how well each aftermarket filter is actually filtering the air going into the engine versus the stock unit. He suggests the increased horsepower could be a result of less filtering going on, especially in the case of the cheaper CarQuest filter—though because he had no way to test the filtering process, that aspect wasn't observed.

Hepa Air Cleaner So, if you've ever wondered if those claims about more power and torque are true, it turns out they are, at least in the case of this K&N unit. Depending on what are you have, gains you see might not be as large (though, either way, we doubt you'll be able to notice them at all).