Old thread but I will add mine. Out of boredom today I filled the tank and hit the highway for a controlled (as controlled as I could get anyways) test. Ambient temperature 6 deg celcius, we are already running winter fuel here, 87 octane with up to 10% ethanol in the tank, wind speed was a sustained 30kmh from the west. The stretch was west of town on a two lane highway with the on ramp for the start in the same spot as the off ramp for finish and a good mix of small rolling road and flats. I reset the lie-o-meter just prior to accelerating to highway speed using about 1/2 throttle or so to get the big girl moving. Cruise control set at speed limit (110 kmph) and let the truck do it's thing. Just my fat ass, a full tank and the tonneau cover with some random scatterings in the RamBoxes. Heading west I was going directly into the wind, coming back I had it at my back. The results show me that these trucks are like trying to push a piece of plywood sideways through water. Two attached images of the EVIC (I used that as a bar so I could see the difference) In short- 14.17 mpg US (16.6L/100km) into the wind, 18.38 mpg US (12.8L/100km) with the wind. 3.73 limited slip out back. I know I'm not supposed to use EVIC but so far it has been within .5 l/100km of my hand calculations either way.