Originally Posted by vasillalov
Well not exactly. Resistance to detonation = AKI -> Anti-knock index. So that's your unit of measurement.
Yes, E85 has additional benefits when it comes to cooling the combustion chamber, but technically, that's different than anti-knock index.
Plain and simple:
USA 91 fuel = 91 AKI
USA 93 fuel = 93 AKI
USA E85 = 94-96 AKI
PURE ETHANOL = 99.15 AKI
Do not confuse E85 and pure ethanol. Totally different things.
Take a look here:
Second paragraph in Octane and Performance Section:
So guys, stop propagating a lie! E85 does NOT have such a high octane rating as you think it does.
There is no lie being propogated. I don't care what the AKI rating is, E85 tunes more like C16 race gas. 100 octane AKI unleaded gasoline cannot come close to what E85 does. Spend some time outside of the BMW forums where people have been tuning on this stuff for the last 5-7 years and you can see multiple examples of how E85 performs similarly to something like C16 or Q16.