Others have run 89 in warm weather and even ran their best times with it at the track. That being said, above 80-85 degrees, I'd run 91 or better. You wont feel the slight hp loss by not running 91+. besides, the warmer temps are killing some power anyway.
Kawasaki recommends 91+ and they designed the thing after all. They should know what they are talking about. It may be that they know how poor the fuel quality can be in some area's so by recommending 91+ they are just covering their bases in case you get a bad tank of fuel.
in any case... when hot out its more likely to need the octane. So run the good stuff, or at least keep an ear out for ping. and definitely don't lug the motor on 89 (or 91/93). Might be too late if you hear it knocking.
after all, its only a buck or two per fill up more. I'm not saying to never run 89. I DO run it in temps under 75, or when I know I'm not going to be in a lot of stop and go traffic to heat soak the motor.
* Last updated by: rod442 on 5/24/2016 @ 3:49 PM *