Until we traded the Charger Scat Pack for this Laramie, we had three vehicles that required 93 octane. That was fine when gas was cheap. But under this current government, it's getting harder to fill the tank. I can "detune" my Charger R/T Daytona and my high-boost PT Cruiser convertible to both run 87 octane. But I'm not buying an unlocked PCM for the Laramie and voiding the warranty on it.
We plan to run 87 octane gasoline in pure or almost pure form in the Laramie. After going through two 33 gallon tanks of fuel, it seems to be fine on Valero 87 octane cooked up in Memphis, TN. Our past experience was that the original 3.6L Pentastar engine was very sensitive to ethanol. So it ran better on pure 87 octane gasoline. But our 2017 Charger R/T was a beast and the 5.7 ran great on whatever we put in it. The engine makes enough timing adjustment to account for it. But that is the real problem. During everyday driving, the 5.7 Hemi has much more power than most people need. So if the PCM detects pinging and ******* the timing a few degrees, the driver likely isn't going to notice. The car or truck will run perfectly fine with enough performance to shoot down the road unimpeded.
***BUT***
If you plan to tow or race a 5.7 Hemi against Mustangs or Scat Packs with 93-octane 392 Hemi engines, you are going to need that extra power you are leaving on the table. The only way to know for sure is to run a science experiment. You will need an advanced OBDII reader and a cell phone or laptop with the right engine diagnostic app that can datalog. Then you drive and datalog the ignition timing retard. Start with 93 octane as your baseline, then burn a tank of 91 or 89 octane followed by 87 octane. This will tell you how the engine is reacting to the cheaper fuel. Since gasoline has many other qualities besides octane rating and ethanol content, you will not be able to depend on someone else's experiment unless they burn the exact same fuel from the same bulk plant and drive exactly the same way with exactly the same vehicle. You will need your own data.
For me, I figure the 87 octane with no or low ethanol will be fine since we won't be towing or hauling anything heavier than luggage. We might step up to 89 octane for trips in the mountains since I like to pass long lines of cars on curvy mountain roads.