S'funny, I just done the very same thing, yesterday evening.
One of my front Zalman 80mm fans was squeaking a little, but a small squirt of WD40 stopped that.
I also connected rear and top 80mm fans direct to 12V instead of PSU's thermally controlled connectors.
What prompted me to take this action was CPU temp had shot up to 63C
After enabling top & rear fans and giving a good hoovering everywhere, CPU temp now back to a reasonable 47C, and that's with a dual core CPU crunching two WU's at a time.
Quite a big difference eh?