E85 Max quantity allowed mixed with Premium?

pistero701 · 2026-05-20T12:25:54-0500

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 · 2026-05-20T12:40:12-0500

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 · 2026-05-20T13:07:43-0500

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

pistero701 · 2026-05-21T11:42:01-0500

2020FordRaptor said:

Thanks bro, does that 30% in the fuel tank makes some difference in terms of adding more power so far?

2020FordRaptor · 2026-05-21T11:59:01-0500

pistero701 said:

Not on factory tune, but if your tune for sure. Big difference when tuned with ethanol.

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E85 Max quantity allowed mixed with Premium?

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