E85 Max quantity allowed mixed with Premium?

[pistero701]

Hello Guys,
What is the max percentage allowed of etanol e85 that can be threated with Premium 91 octanes running stock and with tune for 91 octanes? How many gallons of premium per gallons of ethanol?

Willing to use some etanol in the tank to increase a little bit the perfomance of my ST when running 1/4 mile in Mexico .

Whats your experience?

 

[2020FordRaptor]

It’s not just gallons of it, you have to calculate your mixture. E30 which is 30% ethanol in your tank is the max the factory tune and usually a 91 tune can account for.

 

[UNBROKEN]

Without a specific tune for E50 you’re limited to E30 on a 91 or 93 tune