Switch to 87 and just listen out for 'pinging' from pre detination (spark knock). The engine shouldn't ping on 87 as that is what it was designed to operate on, and the F22 doesn't have high enough compression to normally warrant higher octane fuel... but just in case. Predetination puts a lot of stress on the engine internals.

I actually use mid-grade in my 96 which has almost 209,000 miles on the engine. I started hearing a little pinging one day (the car already had over 150k miles) and rather than try to dig into what the 'problem' may have been, I just switched over to 89 for a few cents more and haven't had a problem since.

I run 87 in the 2007. If it pings, it's going to the shop.