Quote:
Originally Posted by Utah Motorcyclist
It should be the opposite. The lower octane has higher energy potential.
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Octane has nothing to do with power.
Octane is the fuel's resistance to initial combustion under compression... effectively, it's flashpoint.
A higher octane fuel will be less likely to be ignited by a "hot spot" in the cylinder, perhaps from the edge of a valve, or a piece of carbon.
Once ignited, the flame front burns at roughly the same temperature regardless of octane and it will progress across the piston.
The energy potential of a fuel is revealed by it's BTU content...
Gasoline is 114,000 btu/gallon
"Winter" blend is 112,500
E10 is 111,836
gas/ETBE is 111,811
gas/MTBE is 111,745
E85 is 81,800
Ethanol is 76,100
So a gallon of E100 contains 66% of the energy of a gallon of gasoline. It is coincidental that it's octane rating is higher (it's not 150% higher)... that has nothing to do with the energy content of the fuel.