Okay so to quickly summarise: the octane number defines just how explosive the fuel is under compression. 100 means it’s the equivalent of a 100% iso-octane mixture.
The more explosive the fuel is, the sooner it detonates as the cylinder compresses it. If it detonates too soon, at too low a compression, that’s when your engine starts to knock. By adding ethanol you’re increasing the pressure needed for detonation, ensuring that the ignition system ignites the fuel at the appropriate time, thus improve the engine’s longevity.
Okay so to quickly summarise: the octane number defines just how explosive the fuel is under compression. 100 means it’s the equivalent of a 100% iso-octane mixture.
The more explosive the fuel is, the sooner it detonates as the cylinder compresses it. If it detonates too soon, at too low a compression, that’s when your engine starts to knock. By adding ethanol you’re increasing the pressure needed for detonation, ensuring that the ignition system ignites the fuel at the appropriate time, thus improve the engine’s longevity.