Hi Q-Folks, This is a repeat question....every talks check valves, but I would really like to know the answer to this one: "If the oil filter is mounted perfectly upside down (hole Up) and the media is indeed "trapping" particulates, is the check valve found in some filters still very useful?" Thanks.......Paul Royal 1990 90Q20v 1987 5Ks 1967 SS/RS Camaro 1990 Suzuki VX800