I never understand these "on a good run" figures. So what if you get such and such when you're driving to the Mother in Law's and don't want to get there in a hurry?
I do lots of runs though, this week from Norwich it has been, London Monday, Birmingham Tuesday, Brixton yesterday and then it is Solihull Sunday.
It matters quite a bit to me what a car gets on a run at say 85mph, as many get crap MPG doing this if they are not geared right, often worse than I get just pootling around.
I can squeeze close to 600 miles from a tankful out of the E350cgi if I am steady and 500+ not caring.
Also, remember, on a run in a petrol is anything over 2 miles, on a run in a diesel is anything over about 15 miles, quite a difference. Obviously depending where you live.
My average in the E350cdi was 33mpg over the time I had it, my average in the E350cgi is currently 29mpg, (29.4 to be precise) but if you ask me again at the end of the summer I bet it will be over 30 again.
On a run matters, if you do lots of runs, saves the hassle of filling up all the time.