Question: would emissions testing show cleaner burning with 91 or 100 octane in the tank?

Would this be relevant to those who have changed to 100 cell cats?

 

not too sure but my guess would be the 100 octan e would burn cleaner. After all, an octane rating is a measure of the efficiency of how well a fuel burns...The higher the number, the better efficiency so the more conversion and complete oxidation of the fuel into C02 and H2O and the less the CO and other by products.
I will check my Chemical Engineering reference manual for you later.

 

Msindi, sorry but octane rating has nothing to do with how clean it burns.

Higher octane means it can sustain more heat/compression before igniting.

100 octane fuel may be cleaner because the gas companies decide to purify it more, but thats not because of the simple fact that its 100 octane.

 

Octane rating is only a measure of the fuels ability to resist detonation