An air filter is a simple component in the air intake keeping the air going into the engine clean of contaminants such as water, road grime, pollen, dirt & everything else that blows into your vehicles grill. Oil filters keep debris & dirt out of the oil while the engine is running. A properly-working oil filter is critical to a vehicle’s operation, engine life & fuel mileage.Fuel filter is a cartridge located in the fuel line. Inside the cartridge, theres a screen that catches dirt, rust and other debris in the fuel before it passes through to the fuel injector.