My laptop fan was blowing a lot so I reckoned it was time to clean it. When I had finished, the fan was grinding, and unlike on previous occasions when the grinding has settled down, this time it didn't seem to want to stop.
It's an old laptop, in computer years, and it has been left running all day and sometimes all night for many days in those years, so I reckon that it might be time to replace the fan, except that it's a rebranded Taiwanese model with generic components, and a replacement doesn't seem to be available.
Googling the problem suggested it is possible to dismantle a fan and lubricate the shaft, but on my laptop the fan is integrated into the body of the heatsink, and it wasn't possible to put a screw driver under the body of the fan to pop it off.
I decided to try drastic measures and squirted some WD40 round the underside of the base of the fan. On starting the laptop, the grinding had gone, but I began to wonder if WD40 had been a good idea.
I consulted Google again, and what I found was a good example of the value of the internet: everything from wisdom to shite. Isaac Azimov wrote science fiction stories about a computer called Multivac that could answer any question from a terminal in the home. Today we have Google, which can answer any question from a terminal in the home. Unfortunately, you don't get one true answer, you get 10,000,000 answers, ranging from best understanding that current knowledge allows, to utter stupidity.
Some of the better advice: WD40 is actually a water dispersant and not a lubricant. A silicone oil or sewing machine oil would be a better choice. I'd go with that, if you actually have access to the shaft to apply it.
Some of the worst: spray WD40 into the heat sink grill to clean it. This is face-palm bad advice. WD40 is a penetrating and cleaning agent. It will penetrate the gap between the heat sink and the CPU and clean it of thermal conductive agent, to disastrous effect, and penetrate capacitors and other components and have completely unpredictable effects.
What exactly is WD40? Modern science has the answer. Most of it is volatile hydrocarbon that is useful as a penetrating agent, or a water dispersant, or a solvent. The remainder is mineral oil, of various thickness.
Some advice says that WD40 will have no lubricating effect after a few days; some says the thick, non-volatile mineral oil residue will seize the fan; some says that it works.
So, is WD40 a good idea for laptop fans? I'm going with the empirical answer, which seems to be yes. It seems to work. Of course I'll have to wait and see, but I'm pretty sure the volatile hydrocarbons have evaporated, and the fan is working as new. I'm not sure whether this is due to the cleaning effect of the lighter components of WD40, or the lubricating effects of the heavier.
It could be worth a try, if you have a fan at the end of its lifetime that you can't disassemble. Try at your own risk of course.