Thursday, September 15, 2011

• Octane FYI •

I've never understood why people insist on running high octane fuel in an old motor with average compression. Octane ratings do not relate to the energy content of the fuel. It is only a measure of the fuel's tendency to burn in a controlled manner, rather than exploding in an uncontrolled manner or simply, octane is the resistance of combustion under pressure.

The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression and/or heat rather than spark from the plug, it causes knocking. When octane is raised by blending in ethanol, energy content per volume of fuel is actually reduced.

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