I fueled up at the Flying J near Omaha, NE (I-80 west, x. 432) and then drove at 58-59 mph towards Salt Lake City and then Las Vegas. I went around on 80 west to 15 south, bypassing the mountains west of Denver. Still the terrain was pretty hilly and half of the time the wind was almost head-on. I had 41,000 lbs in the trailer and had just installed a full wind deflector on the roof. At my next fuel-up in Springville, UT (just south of Salt Lake), the truck took in 160.6 gallons. Google Maps showed the distance of 938 mi, while my truck odometer said "958". And I know it's lying about 5 miles (shows less than driven), so that makes it 5.7 mpg for the trip so far. Or - if I add those lost 5 miles - roughly 6 mph.
Truck: 2004 International 9400, low pro tires, 3.73 rears, 13 speed, 475 hp/1650 lb Cat C15.
Is this an okay mileage for this kind of terrain and load or should it have been better? As I mentioned, I only did 58-59 mph the entire trip, which made my Cat turn around 1,300 rpm.