Every car has an air filter, and every car needs the air filter to be changed from time to time. Some manufacturers even recommend changing the air filter once a year, regardless of mileage. But is it absolutely necessary to have it done in a workshop?
With this article, we want to show you what you need to consider and how you can change your air filter yourself.
What is the air filter used for?
The air filter does what its name says: it filters the air. More precisely, it filters the air that is drawn in by the engine. In the intake system, the air filter is the first component and is located behind the intake manifold and in front of the mass airflow sensor, whose warm layer must be protected from contamination.
It is also essential that no impurities enter the combustion chamber of the engine, as they cannot burn cleanly and thus damage the catalyst and the engine. The turbocharger can also be damaged by foreign particles, both on the exhaust and on the intake side.
What kind of air filters are available?
In normal series production vehicles mainly paper filters (dry filters made of special paper) are used, as they are very economical and can filter out unwanted suspended particles such as pollen and air dust very well.
Even fine particles and other elements up to a size of 3 µm are no problem for modern paper filters. It should always be borne in mind that a normal combustion engine can easily burn a very very large volume of air.
For a slightly higher airflow, cotton filters soaked in oil from the adjustment zone are available. However, these cotton filters must be re-oiled after each cleaning. Together with the cleaner and air filter oil, cotton filters are more expensive in the long run than regular paper filters.
Where is the air filter in the car?
In principle, air filters are always installed in a dedicated housing that is supposed to retain larger particles. At the same time, the air filter housing protects the filter itself from splashing water. In the event that liquid enters the box, there is a drain at the bottom.
While in the past a circular air cleaner box in the shape of a ring, typical of American cars, dominated the carburetor, today the air cleaner boxes are installed next to the engine or camouflaged as an engine cover.
As a design, there are actually only flat, rectangular or cylindrical filter cartridges, which always have a rubber seal. The only exception is the free air filters, which are freely mounted in the engine compartment without the air filter box. They usually have a conical shape and are found only in the adjustment zone.
The common feature of all air filters is their accordion structure of the filter material. This results in a particularly large filter surface. How do you recognize a good air filter, how much does it cost and when should it be changed?
A high-quality air filter is not just made of paper (cellulose). High-quality paper air filters are recognized above all by their color: thanks to the impregnation with synthetic resin, they are usually yellowish (and not white). Impregnation with synthetic resin ensures that the filter paper cannot absorb water and chemicals.
Paper filters often have an additional plastic film as an upstream filter. If the old filter had such a synthetic layer, the new one should also have one.
Air filters always fit snugly and should not be squeezed or let air through to the side. A good air filter always has a seal that is not too tight and not too soft. In the case of particularly large and particularly heavy paper filters, there are beads of glue on the back to keep the filter paper in shape.
A good paper air filter from a brand manufacturer such as MAHLE, Mann Filter or Hengst therefore also costs between 5 and 30 €. The air filter cotton is much more expensive. They usually cost between 30 and 80 euros and still require special cleaning and care products.
Air filter manufacturers recommend changing the air filter once a year. Vehicle manufacturers, on the other hand, also specify intervals of 90,000 km or 6 years in some cases. Most manufacturers indicate a range of 30.00 km or 2 years. It is recommended that the air filter be changed at each inspection.
Replacing the air filter: step-by-step instructions
Usually, all you need is a Phillips screwdriver and a vacuum cleaner to replace the air filter; for many vehicles, it is enough to loosen the clamps by hand. In rare cases, the screws are opened with a 20 mm Torx screwdriver.
- Locate the filter box. This is a black box with a large hose leading to the engine, or it is hidden by the engine cover.
- Open the filter box. The cover is fixed with screws or clamps.
- Remove the filter element. Rectangular filter cartridges are simply placed inside, cylindrical filter cartridges have a lock.
- Clean and vacuum the dirt inside the box
- Insert a new filter. The filter must not be compressed or twisted.
- Note: Air filters always have an installation direction marked with an arrow on the filter insert. The arrow indicates the direction of the airflow.
- Close the air filter box again. Make sure the gasket is properly seated again.
- The old filter can be thrown in the trash.
How much does it cost to change an air filter?
The cost of material and labor is very low and should cost between € 20 and € 80 in an independent workshop, filter included.
How can I recognize a high-quality air filter?
Visually, lower quality air filter inserts are hardly distinguishable from high-quality air filter inserts. What matters is good workmanship and the perfect fit. We recommend air filters from manufacturers MAHLE, Mann-Filter, Hengst and K&N.
Does a cotton air filter work better than a paper air filter?
The airflow can be higher with the cotton air filter bringing a minimal increase in performance.