Just go with whatever the manufacturer recommends. They always have actual data to back up their recommendation. Its not like they have a stake in the gas companies. If that was the case then every manufacturer would only recommend premium.
I just put Midgrade into my 08 porsche cayenne. Does anybody know what grade I'm really supposed to put in it? I don't have a book . Also what should I do to fix the situation if I'm supposed to put premium in it?I run 100% non-ethanol gas in mine. Running regular or mid grade will cause the engine to retard timing thus reduced power.