Originally Posted by Raeshlavik

Here in Colorado the best we get on the street corner is 91 octane - but at 5000+ feet the lower air pressure going into a NA engine allows for it so it usually works out.

With a boosted engine up here, like the one in my Abarth, you typically start looking at octane boosters or water/methanol injection because pump gas here is expecting 10-12 PSI atmospheric, but the turbo is supplying 20-30 PSI.