Run only what you manual says. As for the E85, I for one wouldn't run that crap in any engine...........

 

Flex fuel

 

With a proper tune, you should be able to get a few extra ponies with E85. The reduced range and possible availability issues would concern me. I would not be concerned with running it in a modern engine...they can handle it, despite what people may claim.

 

I thought it said in the owners manuel not to run E85.

 

There's more to running E85 than a tune. That fuel also requires special fuel lines, gaskets, injectors, etc. E85 is very corrosive and will ruin a system not designed for it. As @Old Dogger said, I wouldn't run that crap in anything though, even if it was made for it.

 

Any modern fuel lines can handle it. Even regular gas has up to 10-15% ethanol. The only thing besides a tune that you may need, is bigger injectors if the OEM ones don't have the capacity for the extra fueling required.

 

I won't bore you with details, because if you're looking at E85 you better already know the details. Personally I'm a fan of the 100-105 octane and better ignition properties of E85, I was about ready to swap my WRX over to it before I ditched it for the Jeep. On FI engines it's good for about 20% gains in hp and larger gains in torque, not sure if it's the same for naturally aspirated motors.

Warranty voiding comments below:
I doubt the stock 392 fuel components can push enough fuel. You'll likely need a bigger fuel pump (or dual pumps), larger injectors and a custom tune from a trusted shop. Possibly a more high flowing exhaust, but I don't know...???

Our sister site Jeep Garage has members that have been tuning SRT Grand Cherokees for years. Might check out that site for GCs running E85.

Good luck, let us know if you do it!! 😀

 

Crappy fuel it is already partially burnt/oxygenated so it makes less power as you get power from hydrocarbon fuel by
It also degraded faster and holds more corrosive water

it is crap for fools that want to support the corn lobby and are foolish enough to think lower price per gallon equals lower price per mile

it is not cheaper and will corrode the fuel system faster