We've just got back from a week on the Isle of Anglesey (very nice and great weather every day) and the MPG on the way there along the M60/M56/A55 quickly reached 60 mpg and then slowly climbed to 69.7. This was in our 500 Twinair 105 with the Sport button engaged all the way and no stop-start. About 16 tons of luggage too!
Overall mpg including days out and the journey home was 56 mpg. Quite impressive, especially as I gave it some clog on those lovely Welsh roads.