I'm finding the motorways are the places for the best results, but I'm usually cruising at 65mph to get good results.
I also notice that its the first few miles that really gobbles the juice, so I try and make a run out of town as smooth a possible, then after 4 miles I start to see the numbers go up.
After 10 miles the figures only improve slowly.
Its one of those silly games I play, and it annoys the hell out of the cars behind me. (Joking)
On A roads I like to move along at about 55 to 50. But I soon get held up by someone in front.
Ans I do find that if I'm in control of the throttle rather than the cruise control I'll do better.