I had a 2010, and I noticed no difference on the butt dyno when going from 87 to 93 octane.
However, with the 2011, I noticed a significant difference -- well worth the price to put 93 octane in there.
On the 10 the 91 octane gives you an extra bit of tq to 335ft/lbs and no official horsepower rating (although one can assume if it bumps the tq up by 10 pts then the HP should be around 325 on 91). There is no performance increase going to 93oct.
On the 11 you only get 377ft/lbs tq and 402hp on 87 so its a SIGNIFICANT loss of performance from the 390ft'lbs and 412hp they rate it for 91 (again i dont think they rate for 93 as its not even legal in california??).
Both models have dual knock sensors and will adjust for cheaper gas to prevent knocking. Both run better on premium but the 11 runs MUCH better on premium.
Temperature has nothing to do with it. Neither does clieanliness. Its more complicated than that. Basically though...it has to do with the more aggressive engine timings and the higher octanes ability to not mis-fire knock at the more aggressive timings/compression speeds. Burns "faster" might be a more appropriate analogy.
According the super tuner Chris.....a 93 octane tune on a 10 would push the hp closer to 340 and a 93 only octane on an 11 would be good for something like 430+ But if you get the tune and run 87 your kinda screwed as your engine will be knocking like crazy which can be damaging.
2011 Shelby GT 500: C&L CAI, Roush GT 500 Performance axlebacks, Steeda 2.65 Supercharger pulley with idler/belt tensioner, Ford SVT Custom Racing Tune, SVT package, Glass roof, Tech package
Gone: 2011 GT/CS Black
Gone: 2010 Sterling Gray GT, Track Pack