When I've checked my Mog's speedo's against the speed shown on the TomTom, usually it reads nearly 10% fast.
This alters the mpg figures produced tremendously!
My 4/4 electronic speedo, compared to my Garmin, is almost exactly correct at most speeds. This is important for a different reason of course - I can't rely on speedo error to keep me safe from speed traps.
When I last checked my 4/4 (1800 zetec) brim to brim I got 42mpg.
NIgel
