Bought a Van......

if we plug in, we can use a microwave and such. Generally, just a small cooler is all we need. I have no ideal on gas mileage, but hoping for better than the '77 Ramcharger 4x4 which got 12-13 mpg on our trips.
What ratio rear?
I have a 12 vdc/115vac cooler that comes in handy for road trips.