Octane and Ethenol
 

I put 93octane in the GC. Unfortunately all of the stations around here are 10% ethanol.



Is the GAS in that blend 93 octane, plus 10% of higher octane ethanol?



Or does the final blend of gas+ethanol have the 93 octane rating? Does this mean the gas itself used in the mixture is lower quality?



Does anyone know how the rating actually works when ethanol is involved?

The rating is for the final blend of gas and ethanol.



Octane ratings are just a reference point, so to speak. If mountain dew were combustible and you tested it, it would have some sort of octane rating. All the rating means, is that this fuel will detonate at the same time as a mixture of X% octane mixed with heptane. Numbers over 100 just means that they extrapolated that detonation resistance.



I hope that answers your question.