On my car I reset the mpg and the trip meter every time I fill up and I always fill up at the same petrol station.
On the OBC the MPG reads that I get 40 mpg, however when I work out the actual mpg (litres divided by 4.546 to get the gallons then miles done divided by the gallons) it works out that I get 36 mpg.
That is 10% out!!
So my question is, which of these is correct?
a) The car is not measuring the correct amount of diesel into the engine
b) The car is incorrectly measuring the miles done
c) The car is deliberately programmed to lie about the mpg to make it look better than it actually is
d) I'm being robbed by the garage of 10% of fuel