On a normal day, when pavement is bare, I usually lock it on cruise at about 110 kph. On highway 2, between here (Edmonton) and Calgary, I run it on cruise at 120 kph. The day that I spoke of earlier was December 18th. The temperature was about -25 C with a -35 C wind chill. As I said, we were doing about 80 to 85 kpm for most of the return 700+ kms. At times we were down to 60 kpms. The truck burned 77 litres of fuel. The mileage figures are all calculated in Imperial measure, so yours would be about 20.
To put this mileage issue in another perspective, my former tow vehicle was a 5.9 L Grand Cherokee which, when towing, got 10 mpg on a good day at 100 kph, pulling a 24' trailer. On a hot day it would over heat with the a/c on. Push it any faster, say to 110 kph and the mileage dropped to about 8. At that weight and size, the Jeep was at it's limit! This truck will haul our new 28' trailer and 1000 lbs in the box all day long with the air and stereo on and get 14 to 15 mpg at 110 kph. And I've got an engine brake to boot! Last summer I put about 18,000 kms on with the trailer on the hitch. The truck paid for itself.