I have owned my 83 240D for the last 4 years and love the car. It is an automatic and very slow which I have learned to drive. My question is at highway speeds it sounds like it is running hard and reving high (relative for a diesel). In GA on the interstates you need to run 75-80 without getting run over. Can this car sustain 80 mph for prolonged crusing?

Also how long do these engines last I see most dying a death before 300k miles. I was hoping to get a 500k miles. Mine by the way only has 140k.

Thanks guys in advance for your time.