If your using Premium in your Shadow, you wasting your money. Only needs 87 octane gas.How can I know that when I press the button and choose Premium, that it really is Premium coming out of that hose? And nowadays it all comes from one hose, not three like it used to be. Around here, at least. So at best, if the last person bought regular and the next person buys Premium, the Premium is diluted by the regular fuel in the hose from the nozzle back to the tank.
Aviation fuel comes in different octanes and is dyed. 100LL is blue, for example.