M6 with just over 3100k. Stock, no mods...yet (other than cosmetic). DIC reports 60.9 km/h avg speed and 11.3 l/100k avg fuel consumption. Checking the last three tankfulls myself I got:
11.17, 10.41, 11.22 litres per 100k.
or 21.05, 22.6 and 20.96 miles per US gal
or 25.28, 27.14 and 25.18 miles per Imp gal
So I would say the DIC is pretty accurate.
There is a great little online tool by the NRC that both Canucks and Yanks can use:
The Fuel Calculator. If you fill up the same way each time it can be very accurate. I just reset the trip meter at each fill up and jot down the figure on the receipt from the gas station, for entry online at a later time.
chromesons you should be able to compare your mileage with the folks in this thread using that tool.