I am averaging high 14- low 15 mpg with 3.55 gears. mixed city and highway miles unloaded. Every fill up, the lie-o-meter is off by 1 gallon of usage and 1 mpg. I fill my truck up the same every fill-up. How can the computer lose 1 gallon of fuel and not account for it? My lift goes on this week with 37's and I predict that my lifted 6.0 with the same size tires will out shine in mpg. Not too happy with the 6.7's mpg but everything else is all smiles.