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      08-31-2012, 12:41 PM   #64
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Originally Posted by Joshboody View Post
I suspect you cannot compare or calculate octane rating of E85 the same as gasoline. The resistance to detonation is comparable to race fuel like c116.
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


Do not confuse E85 and pure ethanol. Totally different things.


Take a look here:

Second paragraph in Octane and Performance Section:
The Renewable Fuels Foundation states in its Changes in Gasoline IV manual, "There is no requirement to post octane on an E85 dispenser. If a retailer chooses to post octane, they should be aware that the often cited 105 octane is incorrect. This number was derived by using ethanol’s blending octane value in gasoline. This is not the proper way to calculate the octane of E85. Ethanol’s true octane value should be used to calculate E85’s octane value. This results in an octane range of 94-96 (R+M)/2. These calculations have been confirmed by actual-octane engine tests." [18]
Examples of this mis-citation can be found at the Iowa Renewable Fuels Association titled "E85 Facts"[19] which cites a range of 100-105, and a document at the Texas State Energy Conservation Office titled "Ethanol"[20], which cites a 113 rating.
So guys, stop propagating a lie! E85 does NOT have such a high octane rating as you think it does.
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