Not quite 45! A drive from Chigwell to Cambridge, about 1hr drive with the whole M11 journey on cruise control at 75mph.
Small amount of local town driving at the end, did see a high of 43mpg before the local driving.
Possibly cruise set at 63mph is the clue as the faster you go there is more air resistance. When the RAC completed its Record Road Trip in the Audi A6 ultra, that particular car’s optimum fuel economy speed was 52mph in seventh gear on the flat.