It tells you in the owners manual, it tells you in the sales brochure. It tells you in some of those decals plastered all over your scooter, and, many of us on this board preach that premium fuel is required, as per Piaggio. Yet, some try to get by on the cheap because that extra 30 or 40 cents on a fill up is going to bankrupt them.
All of a sudden, voila, it runs better when the higher octane is put in! Wow! Call Guinness for the greatest discovery in scooter history! Premium fuel stops engine knock!