My 240D has good compression, properly adjusted valves, and rebuilt injectors. then a year or two ago mileage dropped to 21 or 22. After reading the fuel pressure threads, I made a gauge and tested the pressure per the FSM. Way low. I was lucky enough to buy the overflow valve and a rebuilt lift pump from Greazzer. The overflow valve put the actual operating fuel pressure well above factory minimums. Mileage moved up to 26 to 28. And much more power. Even at 70mph.