I drove from Prince Rupert, BC to Seattle, WA (1200 miles approx) my trip computer said 14.5 mpg but when I filled up and divided the miles driven per the gas I bought I came up with 14.0 mpg. That was driving 60-70 mph and lots of passing slower canadian drivers. I did not baby the truck and got pretty good gas mileage. I had 3 people, luggage and some other stuff in the back, not too bad. Looking forward to what I'll get going uphill to Alaska

Tony in Alaska

 

I don't have the computer, but I would not put any faith into that system.
Take note of the miles and calculate the miles driven and the gallons pumped.
After several tanks, you'll get the REAL amount which is around the ballpark of 10-12 miles per gallon.

 

What axle ratio do you have? What's the configuration of your truck?

 

Yeah I know that the computer is a little optimistic, by .3-.5 mpg . I calculated my mileage in town and on the hwy. In town about 11 mpg on the highway 14 mpg, although not great, but still pretty good for a V10. I have 3.73 gears and 31" tires, V10 long bed, crew cab, 4x4.

Tony in Alaska

 

I have a V10 crew cab short box 3.73 and my computer is almost always right on if I reset when I fill up. I also check it every tank. On the Hwy I get 14.5 to 15 depending how fast if I run 75 alot it is near 14.5 throw in some slower driving and I can get above 15 but I never drive that slow
In town I get 12, with most of the driving I do I average 14 per tank! I do not drive a ton in town.
Draging a 30' 10K trailer that is as tall as an 18 wheeler I get 7.5 running 65 if I push it up to 75 I am in the 6's so I don't do it often. With my smaller 5th wheel I was getting 9.2 on the Hwy.