Your vehicle's air filter is the engines life-line. Improper maintenance can result in engine failure.
A clogged air filter affects your car's performance on a number of levels. It robs your car of power, something you need every ounce of when you're navigating a freeway on-ramp. Perhaps more important is the effect a clogged air filter has on your gas mileage.
Recommended interval: Check the air filter during every oil change. Change the filter when needed, or every 3,000 to 4,000 miles.