How many miles can I get on a gallon of gas in a van
Depends on the van, how well it's been maintained, the efficiency of its engine, and the terrain you're travelling on. Assuming a perfectly flat road with no curves, inclines, or accelerations/decelerations, I'd say anywhere from 10 - 25 mpg.
What kind of van? What year? 7-12 mpg would be my guess.
No way near enough information