Also about the gears my truck is a 3/4 T 4x4 with 4:10 gears but I am a very sane driver with this vehicle I try to keep all my high way driving at 50-55/mph or 80-90/kph
I calculated 10+ mpg with a 14000lb total vehicle load (truck and trailer) on a 600 mile trip (1000 km) trough the rocky mountains of BC in January and a lot of that distance in 4 wheel drive