I recently purchased an '83 300SD. I did not see any wet spots on the engine when I went to look at it or for a couple of months after I bought it. I did my first oil change at 3k and used Shell Rotella instead of the Castrol 20w50 that was used by the PO. I installed a Deutsch oil filter. I typically drive the car to and from work with a top speed of about 50-55 mph and had noticed oil consumption of about 1 quart per 1000 miles. This was with the Castrol. When i changed the oil, I noticed that there was a wet spot behind the exhaust manifold. Nothing horrible but it was still wet. I got on the interstate for the first time since the test drive/purchase and noticed alot of smoke in the rearview. This went away after about 100 miles so I thought that it was possibly related to injectors. Anyway at 120 miles I stopped and checked the oil. It was about a quart low and there was a slight dripping of oil from the bottom of the engine. Also noticed that the exhaust smelled like oil burning rather than yourusual bus smell. Topped it of and came back home.
Opened the hood and removed the air cleaner cover and found a good bit of oil in there. It was in parts of the filter and there was a small puddle in the bottom of the air cleaner housing. Removed the housing and the turbo boost line and there was oil at either end but no obstructions.
Wiped everything out and replaced the air filter. Seems to run better but Makes a little noise when going past 2000 RPM up or down. It had lacked power sometimes and seemed strong other times prior to this. The performance would change from one drive to another. I could go to work in the morning and it would be doggy and then at lunch it would be almost peppy. This does not seem to be related to the ambient temperature. It starts easily at 25 degrees F.
Sorry to ramble but I wanted to get all of the symptoms in there for the gurus.
Thanks in advance,