Still better than my Tmax! On M-ways it all depends on the speed you cruise at - drag from wind increases exponentially with speed. Most of my Tmaxs would give around 50 something mpg on fast roads and travelling at up to an indicated 80 on m-ways (though air temperature seemed to make a big difference). I recall once on a very fast trip to York, on dual carriageways and bombing down a single carriageway on a cold winters day and only getting 43mpg! On a long reasonably gentle run on a hot day, I could increase it to the low 60s.
The computer on my ADV350 is saying I'm getting 76.6 mpg, although I don't take too much notice of the computers, but I haven't had to refill the tank yet! I'm only creeping along the narrow Cumbrian back lanes and carefully navigating the rather twisty and unpredictable main roads and I'm rarely getting to 60mph!
