When we got our 80 240D from the original owner, it was at 305,940K. That was almost 6yrs ago.
We are now up to 388,798. Used 15w 40 diesel rated oil.
At 322K I switched to a full synthetic 15w 40.

Oil use age did not change or did it cause any additional leaks. She uses a qt around 1200 - 1400 miles.
Actually Iam surprised at how dry this engine stays. I do get a drip on the floor now and then.
This engine has not been rebuilt, all original.