
2007 8.1 3500 dually regular cab. Towing this snowcat it averaged just under 5 mpg. The truck, trailer and snowcat weighed right close to 27,000 lbs. The truck was retired just last year with about 85,000 miles on it.
The trucks primary purpose what towing the snowcat. At least 80% of the miles were towing the cat.
Close to 65,000 miles the Hydramatic trans failed. Should have had the Allison.
This truck is what converted me from Fords to Chevys.

Three yeas ago I got a new snowcat and trailer and right at the end of the grooming season last year I got this 2009 F-450 6.4L diesel.
I hit a boulder that had rolled onto the road while towing the snowcat in a blizzard. That kind of ended the Chevy's life. ;)
This truck averages 5 mpg towing the snowcat and climbs the mountain roads at the same seed that '07 8.1 did.
The F-450 handles the trailer better and having a limited slip rear diff it is a lot more aggressive in poor conditions that the Chevy was.