I asked my local Chrysler specialist this question and he said that the fuel computer is calibrated for UK use. So your actual reading is the correct one. Even so for a car that weighs over 2 tonnes and had a 3ltr 24v turbo diesel engine that's still a very respectable MPG figure. I managed to achieve 56mpg on a flat road at 65mph with the cruise control on. Let's see the hemi's compete with that lol