It is important to change the air filter in your car when it gets dirty, for that is one of the jobs the air filter does. Keeping harmful particles from entering the engine and doing internal damage. A dirty air filter can cause reduction in horsepower and gas mileage. STP is a name that has proved itself with quality and price of their products.
What kind of vehicle do you drive? 2002 Chevy Tracker & 1997 Toyota Corolla