Let me be the first to dispel some rumors on octane here.
Myth: Higher octane in a given motor will give more performance.
Truth: Engines are tuned from the factory to run a particular octane. Octane is simply (without going into the mechanics of it) the rate at which the fuel will burn and its resistance to detonation as pressure builds. An engine tuned for higher octane will have its ignition timing retarded to take advantage of the more stable fuel, and also have higher mechanical compression ratios built in. Cam timing is usually set to allow higher cylinder pressure, which in turn requires stronger rods, pistons, etc... Now, an engine tuned for 87 Octane will run worse generally with higher octane fuel. The reason is the fuel will not completely combust because of the slower burn time, and allow maximum cylinder pressure as a result, equalling less horsepower. The fuel is typically ignited BEFORE the piston reaches TDC and maximum cylinder pressure ideally reached just as the piston begins the downstroke. If you use fuel that burns slower than the engine is tuned for, maximum cylinder pressure will not happen until well after the piston is moving down the cylinder, meaning you will not get the "bang" for your buck so to speak.
Equally, by using a lower octane fuel than a motor is tuned for, the fuel could detonate or burn to quickly, causing cylinder pressure to max out before TDC, resulting in tremendous strain on the engine and possibly scattering it (this is why many people who use nitrous and dont tune for it end up with a pile of parts, but I digress...).
In short, unless you know what you are doing and retune for higher octane, use what the manufacturer recommends. Sorry for the long post.