according to my satnav, I average about 289mph since my last reset. not sure what the mpg is on that though…
Mine only does 53 
and at that the steering starts shaking.
Tris:
and at that the steering starts shaking.
It’s a DAF isn’t it ? 
thought my Daf was one of the fastest on the road back in the mid '80s (apart from the Irish lads),cruising along at 75mph…then a couple of ancient ‘A series’ ERFs came coasting by me 