Mpg for Motorvans/campervans

My present Autocruise Rhythm returns on the computer 41.7 mpg on a trip from North Wales to Glasgow, mostly Motorways on Cruise control. On a full trip of some 1400 miles around hilly Scotland and single track roads it reads 38.4mpg.This is as good as my car. This figure seems to correspond to my manual analysis on fuel brought. Is this typical and if so shows that motorcravans fare well with towed caravans