M103 bottom end
My 1988 300 E has 248,500 miles. I had the cylinder head off because of a leaky head gasket at 244,000 miles (it had been off once previously at 130,000 miles, for a valve job). There was NO ridge on the cylinder walls and no evidence of piston wear.
The car also burnt little oil before I had the head off, and since I had another valve job done while it was off, it has burnt none since. My bet is that I'll have to do yet another valve job before the bottom end goes south