I don't believe I would ever spray silicone on the serpentine belt or for that matter any other type of drive belt. Silicone is a lubricant and would cause it to slip a little more. Yes you may benefit momentarily, but personally I don't feel that would be in your best interest. Belt dressing is also a temporary fix. Best bet is to determine why it's squeaking or squealing and remedy that situation. If it's not a mechanical issue such as worn out tensioner, pulleys out of alignment etc, then normally the belt is worn. A shiny belt is usually a good indicator of one that is or has been slipping. It's always a good idea to give the belt a quick glance when checking the oil. Glad to hear the replacement worked out for you.Brett
One thing the silicone spray can determine is if it's a belt issue or something else making noise. One very brief, quick shot right on the belt immediately quieted the noise, which led me to believe the problem was with the belt, not a pulley, or worse. I agree with the above post, though, silicone or belt dressing is not a permanent fix...
A closer look at the belt once it was off revealed glazing and quite a bit of cracking. I'm guessing it was the original belt, with 74k miles on it. I replaced it with a Dayco 3-yr warranty belt, $43 @Pep Boys.
Cheers,
Tom