I've got a Seat Leon Ecomotive which claims to do 76.3mpg.
In reality it gives me a steady 50mpg on a mix of motorway and A road, or up to 55mpg on pure motorway driving.
How they got the book figure is a total mystery to me.
i'd take that car back thats absolutley rubbish, me and my dad both have mondeo tdci's his is a taxi and does 48 mpg mostly town driving and stop start, i did a 400 mile trip at weekend in mine speedo didn't go below 90 and i was getting 49 mpg, if i drive mine reasonably normal on mixed roads i can see 52 mpg on the average trip