I had a boring trip up to stoke on trent (to pick up some computer bits) from walsall the other day, i was in no rush so i thought it would try the "economy" thing...
I reset the trip just after getting on the M6 at J10, and arriving at overclockers 39 minutes later, had covered 32 miles and averaged 49mph (this was the vast majority at 55-60 on the mototway, 2 miles dual carrage and a mile of town) and averaged.....47.7mpg!!! I have pics to prove. (I have the 18 inch monzas and DSG)
I had to go again the next day to pic up some bits i had forgot and had the opportunity of using the "Dad chariot" - an 06 plate Golf 1.6 FSI, using cruise con set at 57mph I got a 56 mpg average.
On both trips the MPG dropped on the return as I was bored stupid from looking at the read doors of Eddie Stowbarts and decided to "make progress", as they say.