To be fair I used to get something similar from my 1.4 which didn't have ACT. Trip computer was also super-optimistic so although it would read 55-56mpg on a long run, when you measured it it was only just over 50mpg in reality.Almost 10mpg more, mine gets over 51 at motorway speed - although I set the cruise a bit higher; set at 70 you are probably doing 66 mph.