Cool, thanks.
Since we're all talking about Octane ratings, I thought I would babble a bit more.
The Octane rating is the % of detonation resistance of pure octane, as measured in a lab. "87 Octane" means that the fuel is 87% as resistant to detonation as pure octane. The higher the octane rating, the more resistant the fuel is to detonation. It does not mean that the gasoline has any kind of Octane in it.
Taking that a few steps further- what it ACTUALLY means in practice is that the fuel is somewhat harder to ignite (which helps it to be detonation-resistant). Therefore, as long as you aren't detonating theoretically you can add a bit of timing since the flame front will be slower- when one droplet of gasoline ignites, it will have a tougher time igniting the adjacent droplet, etc. But in practice you are just compensating for the slower flame front and the extra timing doesn't buy you any performance. What it can allow you to do is run the proper amount of timing for your engine to make optimum power without having to retard your timing to protect against detonation.
Oh yeah, and what it does NOT mean is that the fuel has more power / energy density / whatever. If your car doesn't detonate on 87 Octane, you won't gain anything by running 93 Octane. In fact, you'll have slightly less HP/MPG since you effectively retarded the timing.
The Octane Rating comes from a laboratory test. The "Research" octane rating is done with some archaic motor at 600 RPM. Then they developed a somewhat-more-practical rating system ("Motor" octane rating) of a similar engine running at 900RPM since that is closer to "real world". The two tests will give slightly different results. The gas we buy at the pumps in the USA is called "R+M/2", which is the average of Research + Motor (hence the R+M/2). I think in Europe, they use only the Motor method so their octane ratings at the pump look different. 95 Octane fuel in Europe is NOT the same as 95 Octane fuel in the USA since our rating systems are different.
And don't think you can cheat the system by purchasing 100 Octane fuel a the airport. It will have detonation resistance, but it has an even slower flame front than automotive-grade fuels, since airplane motors typically run at WOT at lower RPM (i.e. 2500RPM). Airplane fuels generally lose power for us automotive folks when you get above about 4000 RPM, compared to a 100-Octane race fuel. It will still work fine, but your HP (torque) will be down. And obviously aviation fuel tends to be heavily leaded to protect the valves.
Auto-parts store Octane boosters are generally hugely misunderstood. A bottle which will claim to raise your octane by three points will raise it from 91 to 91.3. Most people read the "three points" and assume their 91-Octane will become 94-Octane but in reality the increase is barely worth talking about and certainly not worth the money.
In general, blending fuels will linearly raise the Octane level. So if you combine 80% of 91-Octane with 20% of 101-Octane, you'll get about 93 Octane. So a few gallons of unleaded race fuel can give you some safety margin at the track if you would like. (Plus, since the race fuel is rated for automotive use, it will do great at the higher RPM's).
If you want a relatively effective octane boost, you can add about 10% Toluene or Xylene to your tank of gas. I think Toluene is 117 Octane and Xylene is 115 Octane. Both Toluene and Xylene are components of gasoline anyhow, so they won't cause any harm. Gasoline is typically a blend of about 175 components, so if you use too much straight Toluene/Xylene, you will dilute the other active components of gasoline (lubricants, etc.) so you want to consider using real Race Fuel at that point. I've heard of people blending up to 30% of toluene/xylene with no ill effects. However Toluene and Xylene both affect flame-front speed, so if you are tweaking every single HP you might want to play with your ignition timing (but that's probably not worth the effort for 99% of us).