Mixing E85 to boost octane
 

I was recently dyno tuned by Seb from Specialty Z. With map 3 he told me I'll need higher octane. My question is, can I mix e85 with 91 to bring the octane rating to 93-95? My fuel system is stock. Just wondering if it can handle it.

Short answer is NO.

E85 requires more injector flow capacity in general and you really need the E85 sensor in your fuel system so the ECU can determine the ethanol mixture and therrefore "how" much fuel to inject.

But either way here in California, were running an e10 blend technically. Would it really hurt to run it as e20 or e25?

E20 would probably be OK but no a lot more .... best you talk to Seb

Adding E-anything is not a great idea as BGTV8 stated. You might look into blending in some Toulene as an octane booster. I've heard of this being used by some racers in the past but never did much research into mixing ratios and/or safety in modern engines myself. You should definitely do some research before just dumping some in.
-YMMV

DONT add e85 to your 93 octane tune, too much ethanol will cause your AFRs to go lean. I would try some vp 100 "street blaze" before anything.