The air filter in a car generally needs to be replaced every 15,000 to 30,000 miles. There are many factors that play a role in how frequently your car’s filter will need to be replaced, including the type of car you drive, the type of filter in the car, the road conditions you drive in, and the weather elements your car is exposed to. This is why the filter is checked during routine auto service to determine exactly when yours should be replaced. Also, if your car is not driven frequently, the air filter should still be replaced every three years as it can become brittle and crack or break.