Possum- My '84 380SL routinely gets 22-23 mpg at 75 mph (or higher), on the road. I've had to deal the "high idle hell", and a broken door check (an easy fix if you know the secret), changed out the brake pads, fluids, filters, etc. Clock stopped working after I bought it! Problems can be the idle control system, leaking vacuum system, and the fresh air/air conditioning system. The a/c is, I'm told, a very expensive fix, but I don't know for certain. Next project for mine is redoing the rear suspension. Check the car out closely before you buy. Good luck, Ned.