Help, poor mpg

[Mattsmith1989]

Recently bought a mint alphard, 2004 2.4 very clean only 50k miles. was told it would average 30mpg on a motorway run at 60mph, Been driving carefully and even at 50mph on motorways, i have only covered 100 miles and almost half a tank of fuel is gone already! Does anyone know if there could be a cause to this? surely 200 miles with 60 litres of fuel is not right? Does the fuel gauge slow down after half way? any help and advice is appreciated!  

[nov]

Driving in 3rd gear?

[Catweazle]

Check tyre pressures, and for brakes binding....

I get 320 from 60 litres average stop start driving and around 410 with motorways (3 litre)