I wasn't as accurate on my accounting details as you have listed, but that sounds like it's in the ball park for the latest V-10s. Last trip we made, Houston to Las Vegas, in a new 35 foot unit with just over 1,300 on the engine at dealership. I drove at what I call a moderate speed, 63-65 mph with cruise control towing an '07 Focus on a dolly. We got 7.1 mpg for the overall trip. One thing I have found out is that when DW drives she refuses to drive over the 55-57 mph range and she gets from 6.5 to 6.9 per gallon. The tranny down shifts much sooner on the grades when she drives.