My Ford V-10 gasser gets about 12-14 mpg unloaded, and about 9-10 pulling the 11,000# 5er, which works out to be 25%, give or take.
2003 Ford F-350 V-10 Crew Cab 4WD Long Bed
2004 Jayco Designer Medallion 29 RLTS 5th wheel
Bill, Gayle, and Mindi (dachshund)
Retired at last !
Nothing is foolproof to a sufficiently talented fool.