I have an FT/H151 with TT transfer gear. Driving on the flats with nothing on the roof at 60 mph I got over 25mpg. Fully loaded no faster then 65mph I get about 23. Seems like you are running lower RPM.Not sure yet. @SNLC and I were discussing that issue yesterday. The truck seems to be doing very well - as of yesterday it was still above 3/4 after 150 miles. I was hoping for all around 18 mpg but would also like to pleasantly surprised. The cruising RPMs are pretty low.