RE: does it REALLY need 89 octane?
I have HAD to use 87 in my 300C once and it did not like it at all. In fact, I worried about it and ended up adding 91 as soon as I could to "even out" what was left in my tank. This could have been unique to my car, but my advice would be to stick to 89 and know you can get away w/ 87 if you need to.