Just to add my $0.02, I have several family members that really beat the piss out of cars, two of them are contractors and take the MBZ to construction sites daily!!! Despite all of this each one of thier MBZ has gone past the 500,000 mile mark with out any problems other than normal wera & tear. All of thier cars are diesels.
1982 240D, 1985 300SD and a 1985 300D.
Good luck!!!