I have a 1991 350SD. Due to the high compression & poor design of the rods the engine blew 8 years ago. MB is aware of the problem & redesigned the rod to handle it.
MB paid for the repair.
I now have 303k on the car. (The engine failed around 180K)
I do Turnpike driving a lot in Pa. & cruise around 75-80mph. It runs great but uses a qt. of oil about 600 miles.