Ummm...
To my understanding...
Octane increases the initial compustion point (temp) of the gas, It shouldn't slow down the burn, just keep it from igniting before it should.[/QUOTE]
Hmmmmm... this may be largely a matter of semantics but your comment started me thinking about it so I did about an hour of research on the matter at credible web sites (S.A.E., Sandia National Labs, Univ. of Western Australia, US Government, various fuel manufacturers, etc.) and it seems that we are both correct. Most of the explanations were highly technical in terms of chemistry and physics but the most commonly recurring themes that I found were:
1- That Octane
delays the ignition of compressed air/fuel mixtures.
2- That Octane
slows the burn rate of compressed air/fuel mixtures (combustion).
I'm a Physics major so most of the chemistry was over my head. One thing that was unequivocally clear though is that once an engine has enough Octane to prevent preignition and/or detonation (which, contrary to popular opinion, are different things), additional Octane has no beneficial effect upon engine performance and actually reduces power slightly because it further dilutes the air/fuel mixture (displacing fuel) resulting in less potential energy from combustion. To get back on the thread point, I see no way that engine stalls or low idle speed could be caused by changing to a slightly lower Octane gasoline.
