Premium Guard fuel filters offer a wide range of application coverage. They’re made of sheet metal, aluminum or plastic, and are fitted into the fuel line. Dirt, dust and other impurities can enter the vehicles fuel system in many ways. These impurities can clog your engine's fuel filter and result in poor gas mileage, difficulty starting and rough idling. All of which will effect the integrity of the fuel system and the life of the engine. Fuel filters should be changed at least annually, depending on where you live.