Most owners manuals don't tell you what octane to run, they simply say: unleaded gas. If this is the best your owners manual tells you, or if you don't have one, read on. But if it tells you a certain octane of gas to go with, use that, your bike may need a higher octane due to high compression.

If your motorcycle has a turbo, a supercharger, or nitrous oxide injection, then this does not apply to you. You should know all about fuel mapping by now (if you don't learn!)

If your motor is heavily modified, with high-compression pistons etc, you will need to run a higher octane as well.

Ok, so, if your manual doesn't say what to run, you don't have a turbo, supercharger, nitrous, or really high compression, then:

There is a big misconception that you need to run the highest octane you can. This is false.

Octane: the amount of resistance to detonation

Higher Octane Gas: More resistance to detonation

Lower Octane Gas:Ignites easier and produces more horsepower, assuming no detonation is present.

Detonation: basically when the air/fuel mixture ignites at the wrong time and cause a tremendous increase in pressure in the cylinders. If it continues for a long period of time, it can ultimately destroy the engine.

However, most sport bikes are designed to run 87 octane gas, and will not experience any detonation, but will actually LOSE power by running a higher octane, plus it will make it run hotter as well.