At a minimum, engine air filters ($11.50 to $53 per filter, depending on brand) should be replaced twice per year as part of car maintenance. So, if you haven't done so already, replacing your car's air filter is a good idea. When an air filter reaches the point where it causes enough of a pressure drop to restrict airflow, the car's fuel economy, performance and emissions begin to deteriorate, getting progressively worse until the dirty filter is replaced.
"Fortunately, it's easy to replace an engine air filter and, again, it's a job anyone can do without tools," says Travers.
