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According to this answer WD-40 is not a true lubricant. I don't get it - even Wikipedia says

The long-term active ingredient is a non-volatile, viscous oil which remains on the surface, providing lubrication and protection from moisture.

which sounds quite solid.

What exactly does WD-40 lack that prevents it from being a true lubricant?

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    A side note, just because wikipedia and\or marketing material says so, doesn't mean its true.
    – Web
    Jun 1, 2011 at 12:57
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    The "WD" is short for "Water Displacement". No citation but if I remember it was used to get water/frost off and keep it off of space vehicles originally.
    – Mark Schultheiss
    Jun 1, 2011 at 14:31

2 Answers 2

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WD-40 is composed of many different chemicals, and only about 10-20% of these are lubricants. Even then this small amount is only a very light mineral lubricant. Most of the other components are intended to help penetration, but are volatile and are intended to evaporate.

WD-40 does provide some longer term lubrication, but the problem is that the volatile components will dissolve and displace whatever lubricant already existed (e.g. grease), and then the majority of the WD-40 will evaporate. So really it should not be used on anything that requires propper lubrication (or at least, a proper lubricant should be added again some time after using WD)

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  • Would that include Bicycle gears and wheels?
    – JL01
    Jun 1, 2011 at 12:30
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    @JL01: Definitely - the chain contains grease behind the seals on each link, you should only use bike chain lube. Wheels too -anything that has bearings (wheels hubs, crank bearing etc.) shouldn't be doused with WD - if you do your bearings will wear out in no time.
    – UpTheCreek
    Jun 1, 2011 at 12:51
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    Do not use WD40 as a lubricant on bikes. For cleaning, yes.
    – Zepplock
    Jun 1, 2011 at 18:44
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    I use it on my bike U-locks that are exposed to weather -- keeps the lock mechanism moving freely -- I spray into the keyhole and alongside the locking tabs once a month in rainy season. A lock is someplace where I want some lubrication, but not a lot, so WD40 works well.
    – Johnny
    Dec 11, 2014 at 18:48
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Looks like we can finally put this tired disagreement to bed, so to speak:

enter image description here

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    I don't get it; please explain. The image clearly refers to WD-40 as intercourse lube, but how does it answer the posted question?
    – Torben Gundtofte-Bruun
    Jul 20, 2014 at 5:58
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    It actually does not clearly refer to WD-40 as intercourse lube -- it simply implies it. It does clearly state that the manufacturer believes it to be a lubricant for metals. I mainly posted this because I get tired of folks claiming that it's "not a lubricant" or "not a real lubricant," because it does in fact have lubricative properties. It just isn't always a good lubricant, particularly in dirty or wet environments for all the reasons everyone always mentions.
    – Mike Powell
    Jul 29, 2014 at 18:08

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