Originally posted by: GalvanizedYankee
Harvey, WD40 is water dispersant type 40 not a lubricant or penetrant

If one must...use 3 in one oil.
WD40 says lubricant and penetrant right on the can. It was invented as a water displacement solution but that doesn't mean it's not also appropriate for those other uses.
Most fans are sintered bushing type. I think WD40 would actually work better as it's a penetrant and significantly less viscous. That being said - I would spend the $5 and get a new fan before I started oiling anything that goes on my PC case.
I've been twistin' wrenches for > 40 years and WD-40 is a crap lubricant. Rusty gate hinges? Meh! For very short term. Use 3 In One for long term or oil off your car's dip stick

WD-40 works great for cleaning greasy tools in the field or for protecting polished aluminum alloy.