I am a little disappointed that the 5.0 doesn’t get better gas mileage than my GMC with the 6.2 on E85. Also I haven’t felt any more power difference on E85 with the 5.0. With my 6.2 it was noticeable.

 

The 5 L from 2018 on has a compression ratio of 12 to 1 and can use the higher Octane quite well.
You don't give any detail of how much and when you use E85 so my reply is based on having done so and info on the fuel.
It depends on how much E10 and what grade was in the tank when E85 was introduced.
How long you drove etc. to allow the system to adjust.
E 85 very likely is no more than E80 +/- 2 points.
At E ratings above about 35%, E has little value in extra power because at octanes above 100 does not seem to make a big difference in this as a [stock engine].
Tuned is a different story.
The higher the E content the greater the amount of fuel is injected. This is where >less fuel mileage< comes from. The specific Gravity is higher and BTU content is less to achieve the correct A/F for >that fuel.
Bottom line is expect a max of 4% in performance gain if all the conditions are just right. Reference Ford Doc on gas engines, OBDII overview and E85 fuels section.
In these engines, the OX sensor are Air/Fuel ratio detectors directly and feeds their signals to the PCM in the MAP circuit, wherein the software makes the slow changes in injection amounts until the system stabilizes.
The major power increase is from the cooling effect of the Eth and the Octane enabling advanced Ignition timing. The higher Octane slows combustion speed so uses more ignition advance. This tends to increase engine Torque.
Comparing to another engine is difficult to say why the differences are felt when conditions are quite different plus the larger displacement of the 6.2 L engine. 1.2 L is significant difference..
Good luck.

 

it gets significantly worse mileage on E85 vs E0

 

That GM 6.2 is far less 'stressed' than the Coyote from Ford...so it is natural that the performance DECREASE from using E85 would be less than on the Ford engine. The Coyote won't pick up any ponies from ethanol fuel due to the way it is tuned, stock. The old 5.4 did, around 20 hp if I remember correctly, but not the Coyote. Make no mistake, the GM 6.2 is one helluva engine.

 

To the OP, did you test this using a performance meter or are you going off the seat dyno? Even stock, the Coyote will pick up HP going to E85.

 

Performance decrease from running E85? Surely you meant the opposite.

 

I have been on E85 since the dealer fill up. So I am totally on E85.

 

No performance meter but driving both I can feel the difference. I have owned many performance vehicles so I am no amateur to performance. I drove both vehicles back to back so I know the difference. Not trying to be controversy just stating the facts.

 

I'm on my 2nd tank of E85 ever in my '21 5.0. Decided to try something else to see if it helped my misfires under load. I haven't checked again to see if the higher octane has helped but I have noticed that on E85 my truck will climb grades that it used to need to downshift on but stays in 10th on E85. I assume that the PCM being able to run more timing helps the low end torque a lot. Of course I usually average 20 mpg on a tank of 87-89 octane and have been averaging about 17-18 mpg on e85. In my area E85 is only about $0.15 cheaper than 87 octane e10. So you really can't make up for the lower economy, but it may be a good alternative compared to paying for 91.

stating a "fact" based on no quantitative evidence is crazy.

 

I smell a troll thread, the GM 6.2 isn’t even a flex fuel engine like the Ford 5.0. It cannot use E-85 unless modified. So you are comparing a tuned and modded 6.2 to a stock 5.0? Goodbye