On that note... I tried running ethanol free fuel in both of my '97s (from a non top-tier certified station) and got noticeably worse mileage. When I swapped back to E10 from a top tier station the mileage came back. IMO filling at top tier stations is more important than ethanol content unless you're going to be storing the fuel for long periods, as mentioned.
I tried that experiment on my old LX450 and the mileage went way up, but not enough to justify the extra dollar plus per gallon.