I have a '86 420 SEL that leaks oil out of the fill cap. I believe that there is too much pressure in the system. I have checked the pcv valve (or hole) and cleared it. I did notice one time the car burned excessive amounts of oil when it was first started and quit a short time later when it was warm. I haven't noticed it burning oil since. The car does have a rough start for the first few seconds and then smooths out. These are all of the symptoms and some or all of them may or may not be related.