I would have recommended KY or Astroglide if it was a troll thing. Fans have moving parts, so a little lube can help. I use light sewing machine oil, not WD-40 or anything like that. Just part of regular maintainence, I have to do it to my fans occasionally. It can make them noticably quieter, and every little bit of stealth helps.
Here is a handy walkthrough:
http://www.techrepublic.com/article/quiet-noisy-computer-fans-with-a-drop-of-oil/5034842
Here is a handy walkthrough:
http://www.techrepublic.com/article/quiet-noisy-computer-fans-with-a-drop-of-oil/5034842