I've measured it a few times now on a few roads including motorways when they be free so i can do a constant speed.. at least 5-10 miles to get a decent average and with hot engine etc
Cruise seems to pulse.. ie accelerate on and off.. you can't really notice it but you can see it in the instant mpg screen
Plus cruise vent accelerate more than at a glacial pace so i think I'll only use it for 30/40 limits and not for 'cruising'
I have noticed that if you push "resume" and there is a big diff in present speed to target speed it will try to get there ASAP .
I always drive manually up close to set before pushing resume.
I often use the +/- buttons to slow or speed its such a gentle change.
If you watch the "instantaneous" MPG you would never drive a V8, so dont look
J