The reason high octane is called for is the high compression ratio of the engine. Yamaha raised the compression ratio to get the HP out of the engine. You risk knock by running lower octane on hot days or opening the throttle. You can putt around on lower octane if you keep the engine RPM up to avoid knock. BTW, the higher the octane number the slower the gas burns. With a bike running at lower RPM's such as these, a slower burn is more desirable anyway. Even at $0.10 difference in price/gal and these bikes hold 4.5 gal., that's only a $0.45 savings if you are fully empty. I usually put 3 gals in when filling up. I would save only $0.30 to maybe as high as $0.60 per fill-up, not worth the risk of knocking the hell out of the lower end for a few pennies, plus I can open it up w/o fear of hurting the engine.
Do what you want but the high octane is for the high compression.
What's a few more pennies when putting $12-16 in? Just not worth it IMO.
Last edited by TimBucTwo; 07-12-2011 at 09:55 AM.