If you use AUTO it will change to outside air -- most of the time. I actually think I might have seen it switch between the two but I am not sure as I may have changed it without remembers ...

Anyhow, I generally use AUTO and after hitting the AUTO button, I hit the recirc button to use inside air because I have this horrible problem in my area: the darn vents suck in all the exhaust from the cars in front of me and I don't feel like getting gassed.