Which one?
 

Local pump now offers 91 non ethanol. Should I run 93 octane at 10% ethanol or lower octane 91 with no ethanol? 540 blower motor.

If your engine doesn't need the higher octane non ethanol is the better choice.

I've read a little bit on this and some say the 93 with the ethenol allows to be compressed a little more before detonation. How true that is I'm not sure. I wonder if the 93 is just 91 with ethenol added? Wish I could give you a straight answer. Is 93 even available anymore without ethenol?

Some Shell gas stations still have 93 no ethanol, our local Shell used to have it , 2 years ago owner said he had to buy a full semi tank load or Shell would not sell it to him, his tank for 93 octane only holds 5,000 gal. so Shell won't bring it, so much for oil companies.,,screwed again.....