For many people it is more a question of “what is it?” or “do I really have one?” then “do I really need to need to replace it?” For the last decade many of the vehicles on the road have a cabin air filter. It is there to help clean the incoming air into the cabin area. It is usually a pleated filter much like the engine air filter, but its job is to keep dust, pollen, and other fine particles out of the air we breathe inside the vehicle.
Since there is such a large amount of debris in the air these days it is important to check and replace this filter on a regular basis. Even more critical if there are individuals with allergies, asthma, or other health issues involved. Mitsubishi recommends replacing the filter every 15,000 miles or 12 months in normal conditions. It depends on the conditions in your area. Dusty or smoggy areas move the recommendation to inspecting your filter to every 3,750 miles or 3 months. Check your owner’s manual for your vehicle’s schedule.