In article
s.com, Jeroni Paul writes

I've had limited success oiling fans, usually it won't last long as
the oil appears to evaporate or go somewhere else. I tried several
oils for motors and none of them last.

Try a silicone-based lubricant (with a consistency between that of oil
and grease). Expensive but it works.

--
(\__/)
(='.'=) Bunny's thinking about giving Windows 7
(")_(") a go despite what he's said about it...