Yeah, well that enchilada.....Oh, sorry......the bike kind!
Roland's right, as far as I know. 89 is fine, though I'm a still a little brained-washed. My dad always told me the higher the octane, the better, so I still only use the "ethyl"(Man, how old am I? That's 91) But from all that I've read and heard recently, 89 is more than good enough for almost any engine and that you're throwing your money away by going for the Premium Grade.
Dwight