Except that I've never put anything higher than 87 Octane in mi Trail and I get the same mileage that he claims to get, 16-17 in the city and 21-22 on the highway. An ECM's job is to get the most complete combustion possible, based on a number of factors... octane is only one.
Chew on this... Premium fuel seems pretty outdated when ECM's have the ability to prevent pinging or knocking no matter what the octane level of the fuel it's being fed. The whole point of higher octane levels was to prevent pre-ignition in higher compression engines. Since the ECM can prevent that, and the additives are the same across the grades (say Shell 87 vs Shell 91), why bother spending more money for premium?