I got similar the other day. Wasn’t quite as warm but over 40 odd miles return I got about 4.6 which is good, although I was trying.
I do about 100 motorway miles a week now and I set my cruise control to 60mph as I join ?. I’m happy sitting in the inside lane watching the world go by.
I wasn’t always like that. I remember coming back from the Lakes in 1988 flat out in my Sierra Sapphire Cosworth, showing an indicated (and probably very exaggerated) 165 mph. I got my final 3 points from that and a 6 month ban ?. I also got 13mpg ?.