Octane grade for towing

They don't talk about high altitude 84 or 85 octane and don't state what they mean by "normal conditions" nor "some circumstances."  They do warn against allowing heavy spark knock at high speeds and suggest that it indicates service on the engine is needed.

So the the dilemma persists.  Should one buy 87 in "high altitude" states where they sell 84 or 85 octane gas?  

As for premium grade gas, looks like the Chrysler 4.7L, naturally aspirated engines don't drink it, though it'd be nice if they would clear up their ambiguities on the topic.  Seems to me the best source of octane information is the engine maker, since it knows what the engine design parameters are.

You really do need to pay attention to the requirements of the engine. For example, the F-150 has four engine options. Two are normally aspirated (or NA); the 3.5L V6 and the 5.0L V8. Two are turbocharged (EcoBoost); the 2.7L V6 and the 3.5L V6. They all accept 87 octane fuel under normal conditions. However, the turbocharged models recommend higher octane for "severe duty", and specifically call out towing as an example.

In both UT and CO they were using the (R+M)/2 method as is pretty standard in most places I've been.  Thus, my dilema continues. 

I think next time I'll just buy the gas without ethanol.  What I need is an anemometer with a constant graph print out to measure the varying wind velocities, then compare the mileage with the wind factored in.  On second thought, I think I'll just keep cruising along and go slower when I need to.  Eventually, we'll arrive..... somewhere at any rate.