Originally Posted by RockabillSlapMatt

Higher octane is used in high compression motors because the compression can cause combustion just like heat. If the octane is low, it will combust at a lower pressure than higher octane. the pre combustion causes the ping or knock. This can also be attributed to having a motor run so lean that a spark plug heats up like a glow plug and ignites the fuel without a spark.

Originally Posted by TNC

Sounds logical but I don't think it's that simple. Lower octane fuel is more volatile in its nature of how it ignites initially, but it has less uniformity in its burn characteristics from that point on. Higher octane has more stable ignition and overall burn characteristics which is more critical for engines with higher compression and/or more aggressive ignition timing. Now, you know I'm no engineer, but I hope I've learned something over years of messing with carbs, FI, and aftermarket ignition systems. And...I stayed in a Holiday Inn Express last night.