To the best of my knowledget the pcm uses the high octane table till it scences 5+ degrees of constant knock, weither it be detonation or false knock, then switches to the low octane table. It will stay in this table till 7+ gallons of gas is added. So no, the truck has no way of knowing what octain fuel is in it but bases the tables on knock values. So... maybe the tables should be labeled 'good gas' and 'bad gas'. ???

However, I believe Bandit already knew the answers to his own questions already.