+ w/a few of the above...
I have run regular, 'mid grade', and premo of dozens of brands in our '01 3.0, over the past 14 yrs.
Have never had a 'bad tank' regardless of octane or brand, and the mpg has not wiggled much over 105k miles and those 14yrs of the usual stop & go, climbing our mountain road several times per week, lots of trips, etc.
I don't shop for gas, eg driving around to save 20 Cts, nor do I run non-premo to to save any dough: I just buy gas when/where I need it, and pump what 'grade' I feel like using...
Other than an exhaust cam sensor replaced, (code 172, sub menu 12), and a new fuel filter installed for reasonable maintenance at ~ 100k miles, I have not had a 'fuel' hiccup in all these years, running what I feel like running, gasoline-wise.
Anecdotal, and one can pump 91 or 93 every tank, if it makes one feel better about the situ.
By the bye, I had been looking forward to the 'What gas should I/do you use' thread, that comes up on the Jukebox about 3 times per year here, over the past decade.
GL, mD