[Howard]

Hanno,
I take it from what you are saying, that you are assuming that all of the different trucks had the same target revs at a given speed?
I would have thought it perfectly reasonable to expect the heavier trucks to run at higher revs, making use of the available power in the upper rev range, versus the smaller that would be less unhappy chugging along at lower revs.
(Boy, this stuff is difficult to put into words, isn't it!?)
H