Octane is a measurement of the gasolines resistance to knock or ping also known as pre-ignition. It is not better or higher quality fuel. If your engine does not knock or ping with 87 then you are wasting money running a more expensive higher octane fuel. Nor will using a high octane gas give your bike better mileage. That's because the rating refers to how much energy it takes to ignite the gas, (slower ignition equals less pre-ignition) not directly to how much energy the gas puts out.