I called Yamaha on my SHO. They told me to use 89 octane. Advised me not to use 87 and using 92-93 is a waste of money as the engine will not perform any better. In the article that Aussie posted they reccomended using over 90 in the event that some water gets into the gas. They said the higher octane will prevent it from sputtering since it won't be as diluted. I don't know if that is true or not but it was one of things they reccomended. I just put in a water/fule seperator so hopefully that will prevent any water related issues.