I just completed a cross country trip last week and had a chance to check my MPG. I was not towing anything, I had no load, and I was the only person in the vehicle. All MPG calculations were by hand and I filled the fuel tank to the top of the neck (took a lot of patience and squeezing). BTW the cheapest diesel I purchased was $1. 49/gal in Kentucky.
This was all freeway driving. I set the cruise control on 1850 rpm which is about 63-65 mph in 6th gear.
I ran the first tank from full until the low fuel lamp came on:
752 miles, 29. 429 gals = 25. 55 MPG
The second run was intentionally a shorter distance but again filled to the brim at start and finish:
312 miles, 11. 806 gals = 26. 43 MPG
The third run was as above:
469 miles, 16. 321 gals = 28. 73 MPG
Yes, I'm very pleased!