Octane power

["Storhok, Eric (E.M.)" <estorhok@domain.elided>]

Mike
You are assuming that fuel companies add something other than HC's to the fuel to get higher octane.  If they use alcohol derivatives, you are right, high octane fuel does have less energy.

However, if its good high octane fuel, its not what they add, its what they remove that increases the octane of the fuel.  As long as the overall molecular average is C8H18 (which is gasoline), you wont seem much difference in the energy content.  One easy way to increase "Octane" is to replace the Octane molecule (about 30 RON) with Iso-Octane (100 RON), each molecule has the same number of HC's, and the same amount of energy when they burn.  On top of that, they will burn at the same speed as long as it's stable combustion.

Other high octane HC molecules- Benzene, Toluene...  These all have pretty much the same energy content on an HC ratio basis.  And to be gasoline, the overall average is C8H18.

So if you find a power loss with high octane fuel, try to find a different source- as that source uses some oxygenated molecule.

Eric Storhok
Core Emissions and Fuel Economy Team
Advanced Powertrain Engineering
(313)33x75011
MD 35, FPC-B
Ford Motor Company
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