Some one remembered their algebra mixture exercises.

 

really? that's algebra? I thought it was just percentages.

 

Or division.

 

 

And its probably higher than that because although tetra-ethyl lead is banned, the refineries do add octane boosters to gas. And that does not have a linear effect. The additives in the 91 will raise the octane of what was 87 more than their leaving lowers the octane of what was 91.

 

If you look on the pump most gas can be "Up to 10% E85 ethanol" which has a higher octane rating than "93 Premium."

So yes, if you factor in that E85 is commonly quoted as being 100-105 octane and up to 10% of your tank could be E85 you may be above your quoted "minimum octane rating."

But as I stated to the OP earlier, I stay on the better safe now than sorry later side.

 

Ethanol may have a higher octane rating but there is less energy in ethanol than gasoline. Regular actually has more than premium. Octane is a rating on the detonation resistance of fuel.

 

Hmmm... E85 is not 10% eth.

In Oregon 'premium' has only been 91 octane on the pump label. Until the dictator governor demanded 10% eth content - then the labels changed to 92. So its 90% 91 gasoline + 10% eth = 92 octane 'premium'.

 

Yes, but I believe the OP is worried about detonation with low octane fuel, not horsepower.

 

We have 93 and 100+ octane pumps in parts of GA and AL.