I eventually had to give up in attempting to find a specific issue on the millage issue between 240ds. I did not see the same issue on the five cylinder models.

Back then there was a gap where almost nobody was present in it. You either got 25mpg or less or you got 30 or more. This far more recent post shows some examples in the gap area now. These examples may be improved perhaps just with maintenance. As time moves along and we learn more about these engines. It could be worn delivery valves. Other than that one poster that said his 240d never could get more than 25mpg no matter what he did. From brand new. I always found concerning.

What I believe more than I doubt still. Is low fuel pressure to the injection pump creates heavier loading on the 616 engines number one rod bearing. It takes time for this to wear it excessively. Probably measured in years. How much do I believe this?

If I found the fuel pressure low on a 616 I purchased or owned. It is not that hard to plastigauge the first rod bearing. There were a lot of 616 engines that went to the junkyard with that issue.

Catch it early and the crank is probably not scored. They will run seeming okay with low fuel pressure. Yet will run enough stronger to feel it with good fuel pressure. The idle is also quieter and some members said they thought the engine was quieter on the highway as well.