Any decent run I get good mpg, admittedly I don't cane my van, 65mph is about my lot. If I do drive more aggressively then my mpg does drop right off into the low 30s. Last week the catalytic converter light came on, the handbook said to drive slowly to the nearest dealer; seeing as it was Saturday afternoon and I was 150 miles from home I just drove home at 50mpg to the joy of all users on the M6, my mpg was 59.something.
So maybe how you drive might have something to do with the mpg returns you get and it is probably very possible that good economy is possible if you drive appropriately?