After reading many post here on this forum i decided my problem with my 1992 500SEl,w140 series was a bad oil tube cap. Today i removed the right side valve cover and checked them,but found no missing caps.I could not see caps visually so i tried to stick a paper clip tip into them and all seemed solid. The part number was 8 118187 0087 . Are these the dreaded plastic tubes that are common to fail or are they the metal ones? They look metal but a magnet would not cling to them.Do these tubes fail in other ways such as warping? Is it a waste of my time to take apart the left side? My problem is i have good oil pressure when engine is started but as engine warms up,the oil pressure gradually decreases and after a few miles it will get dagerously low pressure.Oil pressure gets better as engine sits and cools off.What other problem do i need to look into? My car has 120,000 miles and has always been cared for. Please help. I need this car back on the road.Thanks