Abstract: A disposable oil filter cartridge particularly designed for use in and with motorcycle engines wherein the filter is arranged within the oil tank of the engine and including a filter retaining body structure for insertion into the oil tank with spring biasing means normally holding the same within the tank and providing a filter passage area defined by the body and retaining the filter portion of the unit and the body defining a by-pass flow area opening under pressure to permit the oil to flow from the cartridge without passing the same through the filter element. The entire cartridge element is removable from the oil tank and is disposable such that cleaning of the same is eliminated.