There used to be a station here that sold "race fuel," which indeed was about 100 octane. A friend of mine once got about 5 gallons and put it in his '69 Chevelle SS 396. He got on it a few times with that fuel in it, and in all honesty, it didn't make a LOT of difference. Definitely not worth the price.

That said, I'd be leery about putting it in a modern car. You gotta keep in mind that the Chevelle was originally designed to burn leaded fuel, so it had virtually no antipollution devices. No telling what that stuff would do to a modern engine.