An air filter prevents debris from getting in the engine as air flows in. Replacement of the air filter is one of the most important components of your car's maintenance schedule. Dirt and contaminants entering your car engine can damage the internal components of your engine. A dirty air filter will cause your engine to work harder, which could mean a reduction in power. We suggest changing it at the car manufacturer’s suggested replacement interval or changing more often if you drive in a dusty environment.