Not long back from a 24 mile round trip to my father-in-law who lives alone. 12 miles each way 90% motorway 60 mph most of the time. first journey 33mpg second journey, after an hours visit, 40mpg. Much better but not brilliant, although, after the mpg I’ve been getting, I’ll take it. Ambient temperature at time of journeys 3°C.
Better but, as you say, not brilliant given that 60mph on a motorway is usually about the most fuel efficient speed for modern cars and most will achieve 50-60mpg in those conditions, but 60mph is slower than most people drive on a motorway. For me, the test of a good engine is the ability to cruise on a motorway between 70 and 80 and not see a massive drop in mpg. I have always found BMW’s to be excellent in that regard (with mpg not dropping much until over 80mph) but our VW drops markedly as speed rises (from near 50 mpg at 60mph to around 38 mpg at 80mph). I would switch the trip computer to another measure other than mpg and just enjoy the car!