Should my Ford Mondeo be returning better fuel economy than just 47mpg?

I purchased a new Ford Mondeo 2.0 Duratorque TDCI (115PS) 6-speed manual in October last year. The car has now done 6,500 miles. The Ford brochure indicates fuel consumption of: Urban 44mpg, Extra Urban 61mpg and combined 53mpg. Although I accept these figures are under ideal test conditions I am very perturbed that I am unable to exceed more than 47mpg. This figure I have calculated during long motorway driving at nearly constant speed of 66mph. I have had the car computer-tested by the garage from where I bought the car, but it has made no difference. I drive very gently with no excessive acceleration. Is the car a rogue car, should it be showing better fuel consumption figures and would I be justified in insisting the Ford garage does something to improve this apparently excessive fuel consumption?

Asked on 3 April 2011 by GB, Amesbury, Wilts

Answered by Honest John
I have actually tested this car over more than 600 miles and averaged 51.5 mpg with three people and their luggage aboard: www.honestjohn.co.uk/road-tests/ford/ford-mondeo-e.../. But we have now set up the Real Life Fuel Economy Register (www.honestjohn.co.uk/realmpg) where owners and drivers can register their own mpg. The system then adds their mpg to a total and divided by the number of contributors to give everyone a better impression of what they are really likely to get.
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