Mpg Figures From The Display Compared To Actual Mpg

[posing]

Was getting 55MPG according to the LCD display but on filling up fully I calculate my MPG to be 48.3MPG (UK Gallons of course). Is this discrepancy a bit much? I understand that the 55MPG is an estimate but is nearly 7MPG difference telling me something?

[Mindings]

Was getting 55MPG according to the LCD display but on filling up fully I calculate my MPG to be 48.3MPG (UK Gallons of course). Is this discrepancy a bit much? I understand that the 55MPG is an estimate but is nearly 7MPG difference telling me something?

A difficult question to really answer as there are a number of potential error sources. Firstly my experience is that it is extremely difficult to gauge how much fuel is left in the tank and how much you put in relative to the topping off point, so there may be a sufficiently large error present when trying to estimate the fuel usage unless you average out over many tankfulls. Sure the display is inaccurate, but then every car I've owned has been inaccurate. I guess mine is about 10% ish!

Phil

[Braindead]

In my experience it's not been that far out. Two things spring to mind....

The shape of the filler neck causes pumps to cut out very easily. It could be that your last "full tank" wasn't as full as you thought it was and when you came to refill this time you got a ture "full tank".

Also, I'd be inclined to average it over several tank fulls so any errors are averaged out.

[Jamboo 1]

In my experience it's not been that far out. Two things spring to mind....

The shape of the filler neck causes pumps to cut out very easily. It could be that your last "full tank" wasn't as full as you thought it was and when you came to refill this time you got a ture "full tank".

Also, I'd be inclined to average it over several tank fulls so any errors are averaged out.

Air pockets in the tank can play havoc...

you need to average it out over a few tank fulls