i have test driven a few of these trucks from dealerships and have noticed a constant practice of putting the overhaed read outs in the metric position.
gives an illution of some fantastic fuel mileage.

 

I reset mine every time and it is off 1.2 mpg to the better than my hand calc.
Almost exactly every time. if different just .1 or.2 mpg.

 

Mine is consistantly off by 3.5 better than hand calc. I reset mine everytime I fill up. Some people say don't reset and it will after several thousand miles be at the corect mpg. Others say you have to reset it when your not moveing or it will be incorrect. I've done both setting and moveing and it's still off 3.5mpg. I haven't tried the several thousand mile thing yet. I really doubt that will make any difference.

 

I reset mine every time I fill up - and mine reads a consistant 2mpg or more high.... Now my Dakota which I also reset every fill up, read pretty accurate, usually within 4 or 5 tenths....

 

I KNOW!!! Every dealer is stealing the 285/70/17 tires that come on the trucks from the factory and puttin 265/70/17 on them and not recalibrating the on board computer. We need to get on this. I want my 285's!! hahahaa

 

My Jeep Diesel shows lower than it really does, 2 mpg every tank. If it's gonna be off, I'd rather it show better than worse.

 

Yep, I reset mine with every fuel-up and when I'm pulling a trailer or when I set out on a trip and it's always about 10% optimistic.