http://www.eforecourt.com/calc_mpg.htm

i use spritmonitor.de (see sig at bottom) does each fill up and also shows average (mine now on 36.5mpg) also can get it to show litres per 100km too.

Surely this assumes

a) your tank is empty when you fill up

you drive till you empty your tank

Is it not just easier to use the maxidot?

maxidot is often wrong, usually on mine it over quotes by 1 mpg but today under quoted by 2mpg. click on the mpg in my sig and it will show you all the details, can also work out if you only put 10 litres in for weeks on end then fill up a full tank. i beleive a few others on here like devontopia use it.

Surely this assumes

a) your tank is empty when you fill up

you drive till you empty your tank

a), - NO

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a) You have to fill your tank fully

use any amount of fuel (as much the amount - as much the precision)

c) You have to fill your tank fully again (recommend filling on the same fuel station and column)

d) calculate MPG - your receipt will show how much fuel you have used between

a), - NO

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a) You have to fill your tank fully

use any amount of fuel (as much the amount - as much the precision)

c) You have to fill your tank fully again (recommend filling on the same fuel station and column)

d) calculate MPG - your receipt will show how much fuel you have used between

Still flawed in my opinion as you have to fill up to the exact same point each time which must be near impossible.

Also, why are people so bothered about such levels of precision (which I'm sceptical you can get anyway)? Ok maxidot may not be totally accurate but it's enough of a guide for me.

You don't have to use it Jonno. No-one is forcing you.

i use spritmonitor.de (see sig at bottom) does each fill up and also shows average (mine now on 36.5mpg) also can get it to show litres per 100km too.

I use spritmonitor (yet to set it up for the new car) and have found it's been bob on with the maxidot mpg readings 9 times out of 10 - even when maxidot's been out its only been by a couple of mpg, so I'd say both are pretty accurate

You don't have to use it Jonno. No-one is forcing you.

I won't, because I have more interesting things to fill my time

Divide your miles by litres and X by 4.546 gives you MPG.

Using filling to the brim and continually adding the miles and the litres onto the the previous total (via XL spredasheet in my case) you slowly built quite an accurate picture of average MPG (slight differences in pump accuracy are evened out).

I have averaged 40.1 mpg over the last 10000 miles in my Octy 2 TDi VRS - the car says nearly 44mpg. I have got 50mpg on long slow journeys but most of my travel is cross country commuting - no long fast roads, just short fast roads

But hey its better than my old discovery TD5 - that did 22mpg.:thumbdwn:

The MFD in my Transporter is usually 10-20% optimistic. Haven't done enough fills in my Octy to see how accurate the Maxidot is.

Another for spritmonitor.de.

You can put all your car costs into it as well as just your fuel used and it works out how much per mile your car costs to run etc.. much easier than creating your own spreadsheet. But then I'm lazy like that.

You can also compare your figures with other users of the site, or if your researching a potential purchase and want real world mpg figures.