Last Oct., when I bought our 450hp Cummins M11 powered 42' tag axle 98 Signature, I drove it from Montana to TX. It averaged 10.1 mpg @ 60 mph @ 36,000 lbs(no toad).
We recently made a 13 day 2000 mile roundtrip in it, from San Antonio @ 1000' above sea level to Leadville, CO. @ 10,200 asl. We towed our 4000+ Lb Toyota. We weighed 42K+ Lbs and drove @ 60 mph. We had a headwind all the way up, and no wind going home. We used the AquaHot during the whole trip, though it was supplemented by electric heaters while at the RV park in Leadville. I have no way of determining how much fuel the AquaHot used.
Driving 1000 miles to Leadville and 11 days of camping at temps as low as -20 we avg 7.0 mpg.
Driving 1000 miles home to TX and 2 days of camping at temps as low as +15, we avg 8.1 mpg.
Conclusion: Weight and headwind kills mpg. DUHHHH!!!
We hope this helps?
Don, Lisa, Alexa, and our 3 doggie amigos.
CURRENTLY MOTORHOMELESS!-Past MHs: 02 Monaco45'Sig,00Monaco43'Sig,99Monaco42'Exec,98Mona co42'Sig,98Newmar38'DSDP(pictured),88FW26'Jamboree .