This external air filter is the primary intake element for the engine air cleaner housing. It captures airborne particulate before it reaches the inner safety element and the intake manifold. A clogged outer element restricts airflow, causing a drop in engine power and an increase in fuel consumption as the turbocharger compensates. The manufacturer’s filter media is pleated to the same effective surface area as the original, which maintains the specified restriction level across the service interval. On installation, ensure the sealing gasket seats evenly against the housing rim to prevent unfiltered air from bypassing the element.