Has anyone done a long term accuracy test on the average MPG reading?
I am finding that mine reads say 56 MPG (UK stuff here) over 150 mile run.
I fill the car to the brim each fill up and record the litres, the odometer
and the trip. I rest the trip and do it all over again. This is not just
one test, but I keep a record of EVERY litre I put in it and I average out
the figures over a very long period of time.
Currently, the trip reads say 56 mpg, and I actually get 48-49 MPG. This 10%
exaggeration is consistent (+/- a couple of percent).
So how do I adjust the reading down by 10%?
I did a distance check on the trip and odometer too, using the KM makers on
our motorways, its accuracy is better than 1%.
For our USA friends, there are 4.54 litres in a UK gallon and a KM is
0.62137 of a UK mile.
I'm not too impressed with the MPG figure as my wife has had a 1994 Peugeot
405 1900 TD for 3 years, drove 40,000 miles and averaged 48 MPG. So I was
expecting 55 MPG at least. I hope its ducks arse syndrome and things will
get better with time.