Yesterday I filled up after a 393 mile run (Midlands to Kent, via Surrey and back (M42, M40, M25, M26, A229, M2 and back). The journey took nearly 10 hours at an average speed of 45 mph sometimes in very heavy traffic. Kept up with the traffic which never got above 80 mph.
It used 48.2 litres and the range said 40 miles left with a low fuel alarm at an indicated 38 mpg.
However if you factor in that there was almost 12 litres left in the tank, at 38 mpg the car could theoretically done another 95 miles, giving about 485 miles on a tankful.
Not bad for a 300 bhp 4 wheel drive car.