Answer: Air filters are one of the most overlooked parts of your vehicle. They play a significant role in the performance of your engine. Your vehicle can lose up to 20 horsepower from a dirty air filter. A dirty air filter can also affect your vehicle’s gas mileage. Air filters have to allow air to pass freely into your engine. If an air filter gets dirty, it can restrict the amount of airflow and make your engine work harder. Your engine requires an exact amount of air and gas to power your engine. If your engine is not getting enough air, it will have to use more gas to compensate. This will reduce your gas mileage as well as your engine’s performance.