Functions of an Air FilterCar Air Filter

All fuel burning engines require a constant supply of air in order to function properly. Air filters clean the air before it is passed through to the cylinders to prevent dust, dirt and other debris from causing any damage.

To put it in perspective, you can compare an air filter with your nose as it filters out foreign particles before the air reaches your lungs ensuring that the respiratory system can function properly.

There is no simple answer as to how often an air filter should be changed. It depends on a number of factors such as how many miles the vehicle has been driven and the environment it is driven in. Vehicles driven in rural or dusty areas may need an air filter replacement more often, alternatively a filter that is more suited to particularly dusty areas can be purchased. This will be clearly stated in the items description.

We recommend that you check the air filter whenever an oil change or service is being carried out.

Benefits of a Clean Air Filter

1. Better Performance & Efficiency

A clean air filter improves the quality and quantity of clean air entering the engine, this improves the engine performance and efficiency. Studies have shown that fuel economy can be improved by 14% with a clean air filter.

 2. Improved Performance

Dirty air filters will not allow the same amount of air to the engine as a clean one would. An engine restricted of air will suffer from a loss of performance and consume more fuel.

3. Extended Engine Life

Regularly changing the air filters is an inexpensive way to extend the life of an engine. Small particles of dust or sand can cause damage to internal parts such as pistons and cylinders.

 4. Inexpensive and Quick

As little expertise or knowledge is required to change an air filter, it is one of the cheapest and easiest servicing parts to fit. Many people chose to change their own air filters themselves. See our How To video below to learn how to do it yourself.

How to Know When to Replace the Air Filter

There a some warning signs that can indicate the air filter needs to be replaced:

  • Black Smoke From the Exhaust
    • As explained above, a dirty air filter can reduce the amount of air getting to the engine. This will cause more fuel to be used in combustion resulting in soot like deposits being sent through to the exhaust system.
  • Rough Engine Noise
    • If the engine sounds like it is misfiring, it could be a result of the soot mentioned above accumulating around the spark plug causing it to malfunction.
  • Poor Fuel Economy
    • Modern fuel-injected cars will become less efficient as it will limit the amount of fuel injected to the cylinder to keep an appropriate air to fuel mixture. The engine will have less power due to the lack of fuel and the driver will have to push the engine harder increasing fuel consumption.
  • Appearance of the Air Filter
    • When checking an air filter it’s important to remember that if the filter is working properly, it will have some dirt on it. The trick is to know when it is dirty enough to be replaced. The best way to do this is by holding it up to a light, if the light can pass through the filter then it is likely that air can pass through it.
Old and new air filter

Old vs New Air Filter

How to Change an Air Filter

Air filters are generally easy to check and replace as the air filter container is usually located on the top of the engine. In the majority of vehicles no tools are required to access the air filter as the covers are only clipped on. In some cases, a screw driver may be required. Consult the owner’s manual or Haynes Manual to locate the air filter of your vehicle. The images below outline the location of an air filter in a 2009 Volkswagen Golf.

vw golf air filter

Air Filter Location


See our How To video on replacing an air filter. 

How to Buy Air Filters on

Visit our Air Filters page and enter the registration number of the vehicle and select Go. If more than one air filter is shown, it is best to check the size and shape of the one currently in the vehicle so you can compare it with the one on our site. The following information is also important for selecting the correct one:

  • Height
  • Length
  • Shape
  • Width
  • Date Limitation: As car manufacturers regularly update the shape of their models; some air filters will only fit particular models of certain years. As an example, the air filter shown below will fit a Toyota Avensis from 1997 to 2003.

Toyota Avensis Air Filter

Click here to start your search for Air Filters Page here. If you have any questions, use the comment section below and we will do our very best to help you.





  • Advance Auto Parts

    For a car’s engine to run efficiently, it needs air – CLEAN air that will be mixed with the fuel. So inferring from its name, it really doesn’t take a genius to know that the air filter is responsible for keeping the dirty stuff (that comes with the air) from getting into the engine.