Has any one compared the fuel consumption figures calculated on the PID to actual consumption calculated from fuel in against mileage?  Mine is over-optimistic by 10 - 15%.  General driving around, the PID always indicates above 50 mpg and frequently above 60 mpg; but the actual consumption calculated by fuel in against mileage over 2500 miles is under 50mpg, which I find a bit disappointing, given that we drive economically.   

I think others on here have said similar....but I've just calculated over 5400 miles and my figure is 59.4 mpg - PID is usually between 60 and 65. Should say that this is open country roads with very little traffic queues etc.

Mines around 7.5% optimistic.

over 15,000 miles swmbo's pid was 7.2% accurate, best was about 3% optimistic, worst was about 10% optimistic, it was worse at higher MPG

 

seem to indicate it had issues reading lower fuel flow rates accurately, not trend over time observed

Thanks for that...sounds like mine is - to quote my dealer - working normally!