I can't find it online in the forums, but I recall that somebody did their own study to see if the higher octane made a difference in their MPG results. Their conclusion, if I recall correctly, was that there was such a negligible difference that it didn't matter if you stayed with 87 as the owner's manual says or put in "the good stuff".

As other discussions here have said, the main things to be sure to do are (a) keep your tires properly inflated; and (b) use the Toyota-recommended oil -- 5W20 or 0W20... not the 5W30 that's printed on the oil cap.