Drove down from cheshire to oxfordshire this weekend and got a massive 41.5mpg over 120miles, one hour and 45mins of driving and an average speed of 51mph. Went on the M6 ->M42 -> M40 and stuck to around 75-80mph. Drove back up before and got stuck in VERY VERY heavy traffic (2hr journey became 3hrs!) and got 35.6mpg in stop and start traffic jam. Quite impressive if i say so myself!