The car’s air cleaner assembly works to provide the engine with a supply of clean, filtered air. Air needs to be as clean as possible before it mixes with the fuel and burns in the cylinders of the engine. The air cleaner assembly protects the engine, improving the performance of the engine, enabling it to work as efficiently as possible while increasing its useful, working life.

The air cleaner assembly has an air filter, often referred to as an air intake filter cartridge, which collects dust and other particles. The air filter is housed in a protective air filter box, which is fixed on to the air intake, enabling filtration at the point the air enters the air induction system. The air filter also helps to silence the car's engine as the sound is absorbed by the air filter.

The air filter has a maximum capacity and once dust collected reaches this capacity you will need to replace the air filter, if disposable, or get it serviced if it is a washable non-disposable variety. Under no circumstances should you clean and replace a disposable air filter cartridge; these should always be replaced.

If the air filter gets blocked due to an excess buildup of dust, dirt and oil, the air stream is restricted which stops the correct mixture of fuel and air needed for optimal combustion. A blocked air filter basically suffocates the engine. It is not a good idea to continue driving your car when the air filter is blocked; this can have serious implications for the heating and ventilation and air conditioning systems as well as causing potential damage to the engine. Dirt and other unwanted debris that enters the engine can seriously damage pistons, carburetor and cylinders as well as potentially causing damage to the air flow mass meter. A blocked air filter can also significantly reduce fuel efficiency. How regularly you need to replace or service the air filter will depend on factors such as how often you drive your car and the length of your car journeys. Climate, air quality and road conditions will also play a big part in how hard the air filter is having to work. If the engine is not performing as well, using more fuel or you have difficulty starting your car it could mean you have a clogged air filter and it will need replacing or servicing.