I run regular unleaded in my 2016 F6B and have never had a knock. But most of my riding is above 5000 feet. Our unleaded at these higher elevations 85 octane (possible because of the thinner air) and never a knock. Now, if I went down to lower elevations that could change. On my 2002 Wing when at lower elevations and on a really hot day I would get knocking when I cranked the throttle, so I would use a higher octane in those situations to avoid the knock. I think 2wheelsforme has it right!