From all the research I've been doing, you can use any fuel you want, but you will get the best performance from 93. I haven't found any reports on the performance numbers on 87 or 89, but I would be interested to find out. At $4.35/gallon....93 would be used sparingly by me!!!!
I'm new to this forum, i found it while looking for Exhaust and Intake systems for my truck. I own a 2014 Explorer Sport in white platinum, i currently use 89 fuel, and see average 17.9mpg to 22.7mpg depending on the weather.