Before they were water-cooled, Saab recommended a cool-down period for their turbos. Now, however, the minimum recommended oil type is 5W-30 semi syn (factory fill & "preferred" type is 0W-40 full syn) & they're water-cooled, so they no longer suggest any cool-down. Typically, you're not shutting the engine off immediately after an extended load on the turbo, but rather driving for some amount of "normal" load for at least a few minutes before turning everything off. If you're both water-cooled & running synthetic, this normal driving period should be enough without additional cool-down.
[Edit:] Oh yeah, I almost forgot. Yes, I agree that any oil which can survive a turbo environment should shine in a NA engine (Toyota 3.0L V6s excepted).
[ March 01, 2003, 06:33 PM: Message edited by: Greg Netzner ]