Like most drivers, you may not think of air filter as part of your routine car maintenance, unless your mechanic tells you that it's dirty when you go for an oil change, or other maintenance issue. But this part is subject to wear and can reduce fuel efficiency and engine life. For every gallon of gas which enters the engine, the air filter provides 10,000 gallons of filtered air for combustion purposes. Outside air is full of dust, debris and other solid particles which stay in the filter. As these clog the filter, it can affect the performance of your vehicle and engine. When your fuel efficiency is reducing or the "Service Engine" light turns on, you will not think it's due to a dirty filter and will search for something else. But keeping a clean air filter is the cheapest and quickest way to keep your car and engine healthy! Issues That Indicate Your Car's Air Filter Is Dirty
If you notice a decrease in your car's gas mileage
Spark plug issues like rough idling or problems in starting caused by too-rich air-fuel mixture
As a result of deposits in engine, "Service Engine" light turns on
Issues with accelerations
Visible dirty air filter
However, if you don't notice these problems you should change your filter according to the vehicle manual, or as recommended by air filter manufacturer, or sooner if you drive through dusty or pollen-laden environments. You cannot see pollen or dust even in direct sunlight, but you have to change it at regular intervals so it performs its job well.