i filled my g40 up at the weekend, done 125 miles since, filled it back up and only managed to get 8 litres back in before the clicker on the pump kept cutting the fuel off. that gives approx 75mpg which is obviously wrong. I didnt use the same garage so i guess that would have an effect, but i doubt i could get more than 2-3 litres of fuel in, so even if we say 11 litres to cover in-accuracies that still gives over 50 mpg. i do drive mainly off boost though