If you are seeking good fuel milage your choice of earlier mercedes diesels is a little limited. Seems the post mid 80s engines generate more power and fuel milage plus are quite a bit quieter. I think the 5 cylinder engine pre 86 weighs in at 800 lbs and the pre 84 240d at perhaps 600 lbs. Combined milage and performance just means newer engines in my opinion. You will probably have to suffer some electronics to get what you want if diesel.