Here in New Zealand we have a choice between 91, 96 or 98 Octane. Prices of each are relative to the Octane rating.
Normally I run 96 octane as it is available everywhere but the other day I happened to be at a gas shop on my way home after a 180klm ride in the wilderness and had no choice but to fill up with 91.

Heading home I expected the performance to be a little down but didn't seem to notice any difference in fact the bike seemed to run smoother when cruising at 100klm (60mph)
Anybody have any thoughts on which is best and why. Common sense would suggest the highest possible Octane fuel that is available. But, is this correct?

 

I have run 91 and 98, had no problems with 91

 

You need high octane in high performance/high compression engine. If you're running a stock engine then any fuel is good.

 

http://www.bajajusa.com/High%20Octane.htm

 

it kinda depends, how is octane even rated with you kiwis.

Taken from wikipedia:
Difference between RON and AKI
Because of the 8 to 10 point difference noted above, the octane rating shown in the United States is 4 to 5 points lower than the rating shown elsewhere in the world for the same fuel. See the table in the following section for a comparison.

i know this is true in a lot of asia states, like japans 96 is basicly our 89 or something close to that. im saying anything higher than or equal to a us standard ( (Ron+Mon)/2 ) 87, your safe. here a link for more info.

http://en.wikipedia.org/wiki/Octane_rating

 

+1

I did that research a while back. The KLX min octane is 91 RON. Here in the US, it is 87 AKI. So next time you are at the pump, check the yellow sticker to see how that rate the octane.

Also, the KLX will handle any octane from 87 AKI to 105 AKI. Ran the 105 AKI once in New York state because of all the heavy engine load I was putting the KLX through. But I mostly run 91 AKI. I could get away with 87 AKI since I have been running the KLX street only for my daily comutes to work.

 

The fuel companies here in NZ uses the RON rating method. The engine on my bike is stock apart from the better air cleaner and the 2Bros slipon. But as I said earlier:"Heading home I expected the performance to be a little down but didn't seem to notice any difference in fact the bike seemed to run smoother when cruising at 100klm (60mph)
Anybody have any thoughts on which is best and why. Common sense would suggest the highest possible Octane fuel that is available. But, is this correct?"

 

True, but it is not. The higher the Octane the more a fuel will retard detonation....lower octane fuels actually have a higher btu/gallon ... its odd but true. So unless you need the Octane or detonation retardance.you should do better with a lower grade....basic physics.