That of course assumes that on both occasions, you filled the tank to exactly the same level, on level ground at the same air temperature.
I always thought the digital read out to be the most reliable. Isn't that similar to how F1 teams calculate their fuel requirements
For the record, my 123 din 1.0 has done 46.3 mpg over 33k miles since new according to the display, which I have never reset. Hope I'm not kidding myself, but that seems pretty good to me.
B Max Titanium X 1.0 125 bhp in Magnetic with built in SatNav and rear sensors.