One very important component to the smooth and optimised function of your vehicle’s engine, is a clean air filter. Dirty air filters decrease the performance of your engine, as it will not allow the proper amount of air into the engine, that it needs to create efficient combustion. If left unchanged, you would likely continue to see diminished performance and eventually, could even prevent your car from running all together.
The air filter is like the lungs the vehicle and can be affected by dusty/dirty environments and even pollen. It is recommended that you change your air filter every 12,000 to 15,000 miles, or once a year. Signs that you may need to change your air filter could be lower fuel economy, reduced horsepower or rough engine running/misfiring.
If you are unsure of the last time your air filter was changed, its probably a good idea to pull it out and have a look or take it to a professional who can advise you on if it is due to be changed.