clearly ECO works best in city driving because that is when there are a lot of starts and stops. That is where you should do your study. The other issue is do you have a heavy foot on the gas with jackrabbit starts or not.
In AZ if you get a black or dark car, I think you are beyond foolish. both of my Mavs have been light colors; and not only are they cooler they don't show the dust.
My 25 Lariat Boost runs just fine in Eco mode. Just returned from a round trip to Taylor AZ (from Mesa AZ), about 320 Miles, high point above 7600 elevation and temps above 105 at lower elevations. I use 91 octane and have plenty of get up and go.
Not seen 93 in AZ, with the heat and my many trips to high elevation locations, I have used top tier 91 year round. I admire the fact that you do most of your own maintenance. At 79, no longer an option for me. Good luck in the coming years.