6 weeks ago coming back from Maldon along M25, M1, M6 etc managed in a Veccy 44.7mpg following an artic for 70 odd mile.
I get more mpg hovering around 4k revs 35 to 36mpg than 3k 32 to 33mpg on a run.
Normal mixed driving Motorway, A, B, C and un named roads at a respectable pace, ie nothing behind me 33 worst case usually 35mpg.
Due to the weight of modern cars theres only one way to drive em, treat them like an old diesel engine, less susceptible to any inclines.