[Big Block Bill]

I do not know what GMC recommends for grade of fuel in a 2011 Denali, but my 2015 Denali XL must run on Premium according to GMC. I agree on a Dyno when the timing can be adjusted, it will increase performance, but in a stock programmed ECM in a late model vehicle timing is set by the factory programming and increasing octane will not help performance, only hurt the drive ability. FWIW, That's my opinion / experience. I make more money on Premium than I do on regular so I hope everyone buys Premium. Not trying to be a know it all here, but in my world it's just a waste of money unless required by the manufacture. Once again, ENJOY the new ride.

Bill