I find that I get by nicely with mid grade 89 octane. Engine runs good and starts good and I don't get any knocking as long as it is not too hot or I am not lugging engine.
i run 93 sams club fuel, it's cheaper than all others in my area and most around here are saying the fuels are mixed with up to 10% ethonal.
sams is still 100% gas no mixing, (they say).
I put only 93 in everything I own. I keep with the prices i.e. best places to buy. If you are not careful some stations will really jack the price of 93. I have found it $.80 higher than reg.
93, major brands if available. Because our 2 cars each take regular, sometimes I forget (yes, I'm getting old) and use that in my bike. If so, I'll add 93 at about 1/2 tank.
Here is Australia we have 92 RON as standard unleaded. Upgraded fuel is 95 or 98 your choice. I run 98 V Power or Mobil 98 normally in an 09 Ultra but would use 95 in a pinch.