Alright this isn't scientific or anything but this is what I came up with. I just drove from near Indianapolis to near Gunnison, Colorado for our annual elk trip. I reset the computer stuff to zero on the personal trip option (DIC).

I have 22,000 miles on my extended cab 2003 with 265 tires.

I weighed the truck empty and with trailer, full tank of fuel each time.

Truck weight with tool box, full tank of fuel, and no people= 6700 pounds.

We ran about 66 mph out there and according to receipts and old fashion math that = 17 mpg. Oh yal the utility trailer is a dual axle that we stuffed 3 quads on with other junk for a weight of 5200 pounds loaded.

Total round trip= 2634 miles

computer says = 14.0 mpg average

receipts and my math say = 14.8 mpg

average mph = 48

computer says 188.3 gallons used

receipts say 190.5 gallons used

There were about 10 times in Kansas that we were bored and kept the spedometer on 60 mph and then started the timer at the mile marker, consistantly we were at about 58 - 59 seconds. So if the spedometer is not already calibrated for 265 tires, then it is pretty darned close.

We were camped at 10,000 feet so says the GPS units we had. I took the truck back on some pretty rough 2 track trails with some really steep hills. The DMAX never missed a beat and I love that allison how it holds it's gear going down severe grades and hills.

The only thing was that when I first started the DMAX in the morning, it would smoke until engine warm up. I don't know if this is a faulty glow plug or what. Temp was around 19 degrees before sunrise. No smoke after engine operating temp was obtained.

The tranny temp stayed below 200 the whole time with the exception of the last 5 miles of the trip going up some really steep 2- track trails pulling the trailer.

This is a stock truck.

I am thrilled with the performance of this truck.

P.S. The Ford 10 cylinder gasser that accompanied us, got 8 mpg towing a 1700 pound pop-up camper.