Oil Problem

This is not a Mercedes but all diesel or alike some are bigger than other.
Problem is My 81 Nissan Diesel uses a lot of oil (199,000 Miles) it allways has since I owned the truck. It does not have any blow-by at all and does not smoke other than diesel smoke. I am thinking it might be valve seals
you think I am right on this. As long as you let glow plugs warm up it starts up like a new one lot better than my benz 300d.

[Knightrider9]

This is where I tell you that not all diesels are alike! If the head in your Nissan is an aluminum casting, then your valve guides are probably shot. Only a mechanic or some persistent digging can tell you this for sure! Remove the valve cover and with the camshaft turned so that each valve is in the "rest" position, see if you can move the valve from side to side. If you can, this is where your oil is going. Remove the head and have your guides knurled and a valve job done! The engine will thank you!