That's what I thought too. After I posted, I figured everyone would come in and tell me how wrong I am.
Redrooster-- Sophisticated computer controls can mask pre-ignition. When it pings, the computer adjusts the ignition to compensate. My parents run regular(87) in their Navigator even though it plainly says "Premium Fuel Only", and you can't tell.....until you put in some premium and feel all the power come back! If you have a noticeable power difference when you run a higher octane, then you need to run the higher octane.
I forgot to post what gas I run. The 4.0 gets the cheaper mid grade(89) or even regular when my wife fills it up. The 304 gets 12 gallons of premium(93) and 2 gallons of 110. I can run just premium, but the 110 is insurance. Shaved heads and steel shim head gaskets. Last year the 110 was $3.48/gal. I think