my folks have a 2004 mercury marauder has about 55K miles and is serviced by ford. About 6 months ago they put a new oil filter adapter on it cause it was leaking. Now my father checked the oil and it was low around 2 qts. No oil is dripping and not smoking and we checked the pcv valves. We cant track anything down and neither can ford. Anyone have any clues what it could be with this car? Its starting to drive us nuts thanks in advance.