The filter cleans the air that goes into the engine, catching particles that could damage internal engine parts. Over time the filter will get dirty or clogged and restrict air flow. A dirty filter that restricts air flow will slow acceleration because the engine isn’t getting enough air. EPA tests concluded that a clogged filter will hurt acceleration more than it hurts fuel economy.

Many manufacturers recommend every two years but say it should happen more often if most of your driving is done in an urban area with heavy traffic and poor air quality, or if you drive in frequently dusty conditions. Air filters aren’t that expensive, so replacing them annually shouldn’t break the bank.