Mark, I agree with your review of the owner's manual specs for fuel. I've heard that about the higher grade fuel adding horsepower as well. I may take a look at the price difference and try it when I've got a good baseline established with regular gas.

2006 Toyota Avalon XLS, Blizard White Pearl, Sirius Radio. Car #75
1994 Chevy S10, Sirius Radio. Car #74