I'm really confused about fuel mileage. My first MB was a 1976 W115 240D, it consistently got 42-45mpg, which was awesome. I measured a few tankfuls driving very carefully, and other tankfuls flooring the pedal (it was an automatic 240, so that isn't saying much), and it really didn't make much difference at all. I never did much maintenance to the car, just got regular oil changes and fixed necessary problems. It even had working A/C (that I didn't use very often, but the compressor belt was never removed).

Now I've got a 1983 W123 200D, which I bought thinking there would be massively awesome fuel mileage. There's not. I got a pretty consistent 25mpg on all-highway driving when I drove it back from Texas. The injectors were absolute crap (when put on the tester they didn't pop at the appropriate PSI, rather they just started a steady stream at about 50-60% of the appropriate PSI), but I replaced them with ones that tested good (original Bosch, not Monarks yet) and it doesn't appear to have made any difference.

I would really like to know how to get my mpg's up to what I was able to get with the W115. In theory, shouldn't I be able to get even better since it's a 2.0L engine versus 2.4L? I think I get better mileage in my 3.0L's which is just bizarre.