Administrator, Resident Tater Salad
Same - my '12 would adjust instantly.I don't seem to have any issues with it taking time to adjust. I'm guessing if you don't run your tank down low before filling up it will be diluted a prevent it from fully utilizing the 91 map.
I saw very little difference between 91 non-E and 93 10%. It was in the neighborhood of 1-2 MPG.