The filter that cleans the air that goes into the engine catches particles that could damage internal engine parts. Over time the filter will get dirty or clogged and restrict air flow. Many manufacturers recommend the air filter be changed every two years, or sooner if you usually drive in major urban areas or in dusty conditions. 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.