what people quote (official figures) and what happens in reality are 2 very different things - as you have found out - Never trust a sales men, or sales literature, it is there only to give you a guide. The conditions that these apply to do not normally bear any resemblance to normal running conditions.
A head wind will make things worse, a tail wind will make things better, fully loaded, speed, accelerating patterns etc. It is unfortunate that someone dupped you into thinking it was better than it should be
I get about 20 mpg for my vehicle, it is 4.5T, this will drop to 16 or nelow if I really tank it, but it will increase to 28mpg or more if take it steady.
But on a 3000 mile round trip you do not want to be travelling at 30 mph other wise you never get anywhere
I agree with you Andy'....as you say there are so many factors that'll influence mpg...
(..Must say though,I'm starting to wonder what the modern day base vehicle manufactureres,Fiat/Peugeot/Ford etc,have been playing at for the last twenty years,if 2lt petrol Talbot coachbuilts, of '80s vintage,are still supposedly achieving 28mpg?!?..)
I'm not getting a great deal more than that from my 2007,2.2hdi Peugeot..
Well,as I posted earlier,I was lucky to get near 25mpg when I ran a 2ltr talbot van conversion,let alone figures pushing near 30..and that was back in the early '90s,when the vehicle was only a few years old..
The figures that you're 'van's achieving would be pretty painful though...