ohnonothimagain wrote: "The X-FIRE, as it stands now, can use any octane"

Not exactly so...pages 149 and 222 of owner's manual specifies 91 Octane, and the label by the fuel filler says use Premium fuel only, which generally means 91 or over.

87 and 89 octane is widely available, and while I know sometimes manufacturers overstate the octane needs for a car, I'm going to pretty much stick with the manufacturers recommendations on fuel.