What is the easiest way to set up a tune for E85 — enable the flex fuel settings or build a dedicated E85 tune with AutoVE?

The trade-off is fuel flexibility versus simplicity:

• Fixed E85 tune: calibrated for one ethanol content. Performance Racing Industry notes this forces you to be particular about fuel, and pump "E85" can be as low as 51% ethanol (eFlexFuel says 51–83%).
• Flex-fuel tune: an ethanol-content sensor in the fuel line reports the blend, so the computer adjusts fuel and timing for whatever is in the tank — and still runs on plain gasoline when E85 isn't available.

Aftermarket flex systems work the same way: Advanced Fuel Dynamics' system re-reads ethanol content 10 times a second and steps injector output up as ethanol rises, so blends adjust without a retune (MotorTrend).

If you'll always fill from a consistent E85 source, a dedicated tune is simpler. If pump blends vary or you'll sometimes run gas, flex is the safer choice. See fuel, E85 & boost.

Want to do it yourself? See who tunes it, and how to learn.