I get about 300 miles from a tank of mixed driving. if all around town, then it is rather poor...
overall average over 4 years of ownership on my 3.0 is 30mpg calculated (rather than taking the on board computer's word for it) and I don't hang about...
What makes a difference on the 3 litre is the sixth gear which is lacking on the 2.5 so when cruising, the engine is quite relaxed.