FYI-
I read in Petersen's off road mag that when above 4000 feet running higher octane fuel has no affect due to Atmospheric conditions that impede the detonation of the fuel. Below there air is denser so running 92+ works because of these principles conversely- I live at 6200 so I run 87 (which kind of kills me cause I luck running the the goods) but I must say I notice no difference in performance, my mileage I might say seems less but I have no precise data to verify. In lieu of not having 92 I use Redline fuel treatment+ 87, which works killer. At sea level I go back to the 92.