I have used the following with zero difference in mileage or driveability.
Phillips 66 87
phillips 66 89
I don't tow or haul anything. I'm getting right at, and once over 20 MPG.
To the original poster; If you know your going to pull something push the TOW/HAUL button and go. I would just use TOP TIER fuel and be done with it.
As I posted before Ma Mopar tech said they assumed 89 octane had more detergents so thats why they "preferred" the 89 stuff to keep engine cleaner inside. I believe them.
Just my 2 cents.
2014 Express 3.6/8 speed/3.55 gears...Work Truck
2012 Equinox 2.4...Wife's Ride
"Life's hard, it harder if your stupid." How would you know?