Originally posted by: LoneWolf15
In a small sleeve-bearing fan such as a GPU fan, too thick an oil will be more likely to gum it up, and some oils are known to soften plastics as well.
Show me a fan that failed because of this "softening plastics" theory? The only place where that would be a problem is if the oil were to sit soaking into the support struts connecting the hub to the frame. Elsewhere there is lower stress, more plastic, it wouldn't matter in use. It would be VERY hard even with far too much of far too thin a lube, to cause multiple struts to be soaking in oil long enough to make a difference. It would be ever rarer for the fan to use plastic effected by common oil/lube, they ARE aware when they design them that there will be oil in the bearing.
Thicker oil will not "gum up" anything. You might be thinking of too thick a grease, OR perhaps too thin of an oil that ran out and softened up the adhesive on the label due to a non-sealing plug.
A thinner oil won't last forever, but more can be added over time if necessary.
Nothing lasts forever, but the fan will keep wearing out with the thin oil, and it will have to be applied roughly 4X as frequently, perhaps even 10X. I have fans lubed over a decade ago, once, still working fine.
I have used either light oil, or light to medium weigh bearing grease (i.e., white lithium grease or teflon-fortified bearing grease) and both have served me well. Admittedly, on a larger fan such as a 60mm-120mm case fan, I would use a heavier lubricant.
Bearing grease is for bearings, should only be used to repack a very large (larger than anything in a PC) ball-bearing, not a sleeve-bearing. You're using two opposite extremes instead of the correct lube. Larger fans do NOT use a heavier lube, they're typically better balanced and have deeper bearings, if anything they could last longer between lube intervals with a thinner lube, all other things being equal, only differences being due to the size of the fan.
Either way, we can both agree that WD-40 is bad, right?
Yes, WD-40 is bad. It should only be used in a situation where the fan "must" run immediately and there is no other lube on hand. That is not a common situation though, a used drop off of the typical car's dipstick is better so long is it's not severely contaminated, enough to look it.
By the time a fan needs lubed, it's typically making noise. There is more play in the bearing and perhaps inbalance that accelerated the wear. The lube must provide the thickest film strength reasonably possible to reduce wobble as much as possible. Wobble is going to be the far largest cause of wear once the bearing is deformed as it would be by the point a user realized a fan "needed" lubed. 2nd most problematic is run-out. It must run back out of the bearing as little as possible, not only due to gravity but the already present-wobble and even the tiny bit of inbalance present in any fan, especially a small/thin fan, though particularly once it has worn enough to be making noise or having significant enough RPM reduction that it dropped below a threshold to become noticable.
On the other hand, if we were to contrast a very large, high precision fan bearing, perhaps even one having a felt lined oil-well, it should instead use a thin oil IF the fan is relubed on a regular interval
before there is significant wear to the bearing. Even larger fans might have no greater precision but by percentage due to their overall size, and could get away with a thinner lube to due greater bearing area allowing thinner film to suspend the shaft. Even so, too thin a lube would still reduce the lube interval. Remember I am not suggesting a thick grease, rather a very thin grease, only thick enough that it's drop-point is exceeded by increase of environmental temp over room temp, if it weren't already above it's drop-point at room temp. In practice a consumer is not going to be able or willing to go to this trouble determining drop-points of lubricant so the simplified term "thicker" oil is used instead. There is a tradeoff to be made though, IF the fan were in almost perfect working order then it's RPM might be reduced a slight (typically less than 5%) bit by the thicker lube, except that if one isn't very diligent in lubing the first time and each subsuquent, there is already enough bearing wear that any potential RPM reduction is offset by the RPM increase seen by reduction of wobble.
A properly lubed fan may not need relubed for a decade or longer. The lower quality and size fans often seen on video cards, and those mounted non-vertically (a sleeve-bearing fan is meant ONLY for vertical orientations unless specially, unusually loaded) may need lubed more frequently, but the lowest freqency and least wear comes from the thickest oil lube possible.
