Dissapointed with fuel consumption at motorway speeds.

[gen2c4s]

Our 30d m sport delivers around 34 mpg at a steady 55-60mph but at a steady 80mph this drops to 29mpg, our old e53 at a steady 80 would deliver 32 and an overal 26mpg including round town driving.
The E70 seems to be mapped for 55mph as around town its useless and at 80 its useless. My C4s is returning the same on an urban run.
Not impressed if this doesnt get better with miles!!!!!