I am considering looking for a used non-diesel Mercedes here in LA. No problems generally with the bodies because rust is usually not a factor. How long can the engine from say the 1988-89 Mercedes go? I've seen some with 130000-200000 miles and wondered if that's pushing things a bit.
It depends on how lucky you are. What model is this? 89 Mercedes typically have a wide range of stand deviation, which didn't get clamped down until the mid 90's. If the car ever breaks down, you can get the parts within a week if you are lucky plus they cost 3 times more.
The most common problem on the older Mercedes V8(not diesel) engines is that there are plastic guide rails that have a tendency to destroy themselves over time. When that happens, it's more than likely for a piece of the rail to become jammed on either the cam gear or chain, and that causes BIG TIME engine damage. If the car hasn't had the chain guide rails changed, i'd would change all the components: rails, chain, and tensioner. It does cost a fair amount of money, but it's cheaper than a new long block. Another problem is snapping radiator necks, it has been fixed with either a new OEM Behr radiator with steel inserts, or a aftermarket radiator with a stronger resin. If the radiator has been changed, do yourself a favor and use OEM Mercedes coolant or Zerex G-05, green stuff is BAD for a Mercedes.