My on-board computer tells me that the car consumes an average of 5.2 L/100km (that's about 45.5 mpg) whereas the real value (calculated from the gas bill and the trip-meter) is rather 7.2 L/100km (~33 mpg). Is it usual that the computer's value is completely inaccurate, or do you have accurate values from your computers (if you have one of course) and mine is somehow malfunctioning?
Matthieu