Bumping the thread as I have a related question: On Wed I'll be 9 days into a 22 day one-way rental. We have a minivan now but after Wed it'll be silly to have such a large vehicle.
We are now in the destination area, can I just stop in and ask for a downgrade to a sedan? My 'complaint' is the MPG and/or handling on mountain roads. I'd be at the Avis main airport location so barring any surprise event in the area, they should have a decent supply of vehicles.