7 thou + 200 miles= no oil leak

Finally - problem is solved. The mysterious puff of white smoke from oil hitting the exhaust on the rear passenger side of engine on 1988 560 Sel is cured. After trying 3 valve cover gaskets and much checking - I gave up and took the car to Mercedes dealership and after 2 hours they determined a warped valve cover causing the problem when the engine was hot. I sent the valve cover to a machine shop and they had to mill 7 thou of an inch off the bottom to straighten it. Cost was $70 CDN (about $45US) . Still skeptical , I reinstalled the cover and torqued the 4 valve cover bolts to 4 Ft/Lbs. After the initial burn off of oil that that leaked out when the valve cover was removed - the problem is solved! No more oil leak. 200 miles later - still cured!! Hard to believe that a .007" warpage could cause the problem - but it did. Hope this helps someone else with a similar problem. Just as an aside - the tech at Mercedes said that it was common for valve covers to warp on diesels but rare on gas engines. Forgot to mention - the oil leak never started until the engine was at operating temp. I guess the warpage got slightly bigger as the valve cover heated up causing the leak to start. It's great not to smell burning oil in the cabin again!