Octane as recorded at the gas pump is a measurement of how fast the charge of a particular fuel mixture burns. It does not measure fuel quality, nor is there more power or energy (BTU's) in high octane fuel. It is based on the burn characteristics of a particular chain of hydrocarbons, 100 octane being the number assigned to a fuel composed only of that certain combination (chemistry majors feel free to add information here).
But that is ALL it means. The timing advance curve of your car is set based on the idea that you'll be running whatever octane gas is recommended in your owner's manual (usually 87 octane gas). Unless your engine has fairly sophisticated detonation sensors that can adapt the timing of the engine to match a different fuel, you are just wasting money.
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"If you hit them hard enough, anyone will put the ball on the ground." - Bronco Mendenhall