DevonDave

I often do a trip from Devon to Yorkshire and usually achieve an average of 45mpg.  Driving around locally with a mixture of town driving and dual carriageways I average around 40mpg.  I am always gentle on the accelerator and certainly don't drive like a boy racer.
 
I have found that the most economical speed is around 60mph, although that would be impractical on the motorway.