Here is a better breakdown in numbers.
1st leg of the trip I didn't drive at any steady rate of speed because I only had 354 miles on the odometer, so the numbers will be slightly missleading, due to breakin procedure, traveling uphill from Ca. to Utah.
535 miles-38. 359 gallons= 13. 96 MPG/ overhead 14. 4 MPG
2nd leg of the trip I drove the speed limit at 75 MPH which was mostly flat through eastern Utah desert, and some climbing through the Rockies into Denver(Aurora-Flying J)
505. 9 miles-31. 980 gallons= 15. 82 MPG/ overhead 16. 2 MPG
3rd leg of the trip is going to be a little confusing because the numbers are way off for reasons I can't explain except for the elevation in Denver at 5K above sea level. This is mostly downhill on a slow drop of elevation to Wichita Kansas. My overhead was showing only 10 MPG when I left the Flying J in Aurora CO where I filled the tank, and my injectors sounded like I was climbing a 6% grade with a load, I even pulled over to check the truck for any issues and found none, even checked the airfilter, the MPG was slightly increasing as I droped in elevation. I stopped in Burlington CO. and filled the tank again incase it was due to bad fuel.
Burlington# 155. 6 miles-12. 680 gallons= 12. 27 MPG/ overhead 13. 4 MPG
Wichita# 350. 3 miles-15. 902 gallons= 22. 028 MPG/ overhead 16. 9 MPG note: the tank did not fill all the way when I thought it did, reason for the next set of numbers being off as well.
The next bit of info is some city and HWY driving. I had to take my wife to KC airport, for her flight home, from Chanute Kansas where I stayed for 5 days getting the bed installed. It only took 1/2 day for the install, we just wanted to tour Kansas until her flight home. so this leg of the trip is all flat land low elevation driving.
337. 6 miles-30. 150 gallons= 11. 198 MPG/15. 6 MPG note:see above note.
Now some of this driving doesn't include the weight of the bed but it is 50%of the miles, so I will declare it as 50/50 with bed weight
281 miles-18. 519 gallons= 15. 9 MPG/ overhead 14. 1 MPG
The rest of the trip now has the weight of 9150 lbs with the bed, on the return trip and now is climbing slowly up hill to Burlington CO. , where I filled up so I might possibly see why I had such terrible MPG before through Denver.
374. 6 miles-33. 519 gallons= 11. 18 MPG/ overhead 11. 9 MPG
This leg is all climbing from the Colorado/Kansas boarder into the Rockies in Frisco,CO. , where I stayed for almost 2 nights. I did want too ski for 2 days but the threat of 1 foot of snow for the next day, after skiing all day, changed my mind, and I left at 3:30PM to avoid the slow driving if it snowed.
238. 3 miles-19. 874 gallons= 11. 99 MPG/ overhead 12. 9 MPG
this was the longest part mainly due too skiing all day then driving over 500 miles into the nite, and it mostly is all down hill driving from Frisco,CO. , except for the Green river Canyon in Utah where I believe they should test drive all trucks up that grade in the summer. I counted at least 4 runaway truck ramps going east, down the grade.
452 miles-30. 703 gallons=14. 72 MPG/ overhead 15. 5 MPG
This last part is the home leg and I drove the truck until empty at home for the weighing of the truck for DMV so I pumped 5 gallons too make it to the scales and this is mostly down hill too.
787. 4 miles-56. 268 gallons=13. 99 MPG/ overhead 15. 1 MPG
These numbers are at the speed limit through out the trip except as noted in the beginning, and the overhead computer was fairly accurate and I will believe it from now on unless I take another trip, when it is more precise.