I paid $1.68 for 85 yesterday and the fillup was under $27.
When you 4th gen guys use the higher octane do you notice an increase in MPGs with 91? Powerwise the only way you'd really notice is run it at the strip or get a dyno since I'd be curious how much of a diff it really makes since butt dynos seem to be affected by people justifying the extra money they spend like on throttle body spacers which don't do anything but people swear they feel the added power.
I have heard that running premium with the 4th gen V8s isn't a nessesity but there is a bit of a real power gain from running 91 or higher.