[MOTORHEAD]

Old Dog:
I would be happy with 12mpg (no,not really), and being in general aviation for 45 yrs, I understand the aerodynamics of the box type trailer. I am planning to do some re-shaping on the front of the trailer a-la Pete Brocks "Aerovault" car hauler. Love to have one, but don't have 30K to spend on something that doesn't get used very often.
My problem is that I used to get 12-14 with the trailer, and much more @ slower speeds. Something has changed,and I think it's an alignment situation regardless of the trailer shops opinion (" it's not so critical on a trailer") Maybe on the little two wheeler from u-haul, but on a multiple axle 5klb + loaded one, i think it is.
The only other factor I can think of is the truck itself. Still get 20-22 mpg @ 70mph without trailer, but maybe engine is a little down on power, but not enough to make a difference without the trailer, but is struggling with the additional load.
At only 164k mi, the engine should be ok, but will run this question by my local diesel guy.
Thanks for your input.