Scania R470 Fuel Consumption

Unbelievable mpg figuires,i know of one n.irish company which had 1854 mercs and never pulled more than 6 tonne.6.5 mpg was the norm,and it wasnt the mercs cos now they have changed to R480 toplines same work same drivers and weights.the figuire now is 7 but they reckon its cos the scanias are opticruise.