I personally wouldn't risk it just to save a few bucks. Fortunately, I live in a state where 100% gasoline is widely available and only use non-ethanol fuel.

 

This table on page 60 of the hybrid supplement specifically says E15 is OK for the 2.0L engine. Ethanol has about 2/3 the energy content per gallon of gasoline, so in theory you'd get about 95% of the mpg of pure gasoline. (Most gas is E10, which would be about 97% the mpg of pure gasoline). That said, I've never tried E15 because I've never seen it in Texas.

 

I've used U88 (E15) in every Jeep we've had where U88 was available. The energy deficit is actually not quite 100% because the engine can also tune differently as it adjusts for the different fuels.
I've towed with it (my JTs) and have used it in our 4xe and Grand Cherokees.
I have yet to see a noticeable difference in mpg. Towing with U88 in my JT gives me almost the same mpg with 5,000 pounds behind that 3.6
That tells me the PCM can adjust and deal with it.
ISU has done testing on ethanol blends for years - starting over a decade ago with testing 15% in various vehicle and found that the difference seen was between pure and 10% and that the extra 5% really didn't matter to most modern vehicles.
I've had no issues at all.
Would I park and store a vehicle long term with higher ethanol content? Only if it was sealed and any air in the tank was dry. So I won't leave it in a classic car any length of time, nor would I let my JT sit for months with it, but for running and running the tank through in a couple of months? Meh, no problem here and I see no difference in mpg or power.
Ethanol burns well because it is an oxygenate, meaning that ethanol molecules contain oxygen.
And - it burns cooler, the flame temperature of ethanol is more than 40°C cooler than gasoline, meaning lower chamber temperatures and less chance for detonation - leading to the ability of the PCM to advance timing.

 

I've used U88 (E15) in every Jeep we've had where U88 was available. The energy deficit is actually not quite 100% because the engine can also tune differently as it adjusts for the different fuels.
I've towed with it (my JTs) and have used it in our 4xe and Grand Cherokees.
I have yet to see a noticeable difference in mpg. Towing with U88 in my JT gives me almost the same mpg with 5,000 pounds behind that 3.6
That tells me the PCM can adjust and deal with it.
ISU has done testing on ethanol blends for years - starting over a decade ago with testing 15% in various vehicle and found that the difference seen was between pure and 10% and that the extra 5% really didn't matter to most modern vehicles.
I've had no issues at all.
Would I park and store a vehicle long term with higher ethanol content? Only if it was sealed and any air in the tank was dry. So I won't leave it in a classic car any length of time, nor would I let my JT sit for months with it, but for running and running the tank through in a couple of months? Meh, no problem here and I see no difference in mpg or power.
Ethanol burns well because it is an oxygenate, meaning that ethanol molecules contain oxygen.
And - it burns cooler, the flame temperature of ethanol is more than 40°C cooler than gasoline, meaning lower chamber temperatures and less chance for detonation - leading to the ability of the PCM to advance timing.

That’s for a JT, the 4xe JT hasn’t been released yet, so you are talking about a standard powertrain. 4xes can go months on 1 tank. The potential is there for moisture to collect in the tank. So for phevs I would avoid ethanol if possible if you know you wouldn’t be burning through it anytime soon.

 

It seems we've settled that the 4xe is required/designed/spec'd/programed to run E-15.

I've probably run it. I pay zero attention to ethanol content. As long as the gas station is modern/well kept and preferably a known brand/franchise I am comfortable putting my octane of choice in the 4xe.

 

I have 105,000 miles on my 2020 Cherokee Trailhawk with the 2.0 turbo. Over half those miles have been ran with e15 88 octane. I run it regularly in my GC TH 4xe as well, but my "commute" means I run through well over 1 tank of gas per week.
I do not use e15 in my motorcycles unless on a trip due to long term storage concerns