Not to muddy the waters but isn't a lower octane rate fuel just more likely to pre-detonate, i.e. knock?
So the worst that would happen is the engine knock sensor would detect knock and retard the ignition timing and prevent damage.
btw, I read an article in the Toronto paper stating the highest available octane fuel available here (94) is created with the help of ethanol.
http://www.thestar.com/wheels/articl...rmance-engines