If it's a concern you could always drain the tank and then pour that into your closest car's tank. I bought a new in '08 FG fastback tank from Burton's Bike bits. They said it was made with ethanol-resistant resin but I Caswell-coated it before filling it the first time anyway. No signs of any problems yet. I have always used 87 octane in my Commando with no sign of detonation using factory-spec timing setting. As noted, performance-wise , higher octane fuel than the engine needs won't do anything but lighten your pocketbook.