There's so much mythology here.... read up on the subject: http://www.faqs.org/faqs/autos/gasoline-faq/part3/ In short, Octane is a measure of the fuel's resistance to pressure induced detonation, nothing more. It has nothing to do with energy content, ignitability, flash point, vaporization rate, burn rate, burn temperature, or anything else whatsoever. However, all those characteristics do vary from one fuel type to another- pump gas has entirely different characteristics than AV fueL or race gas, and among race gas there are dozens of different permutations... Same with pump gas from season to season. My hazy memory is that the higher octane fuels, due to their greater resistance to detonation, do have less ignitability, higher flash point and less energy content. That decreased energy production is more than offset by the ability to run more compression and timing, for more hp.