It is lots easier to know why it doesn't work than to know why it works.
I'm still baffled by those things. For instance why does my sliding door slide lots easier when I spray "the hard to reach nearly fully enclosed wheels" with WD40?
I mean I have to drag it before spraying and when I sprayed it I have to stop it smashing in the lock.
Correct.
And the "WD40 company" thrives by that, as you will need to reapply it over and over again, until something is dissolved too much, and fails forever.
polymorph:
WD40 is not oil. Too many people treat it like it is.
That's not what the Wikipedia link says.
"WD-40 is primarily composed of various hydrocarbons."
"The long-term active ingredient is a non-volatile, viscous oil which remains on the surface, providing lubrication and protection from moisture."
They state the MSDS sheet says "<25% petroleum base oil, presumably a mineral oil or light lubricating oil."
I've seen hinges destroyed with it, because it washed out the original grease and what it left was insufficient. I've seen rotating bearings destroyed for the same reason. I've seen potentiometers and switches ruined by it.
It has its uses. But in my experience, it sucks as a lubricant except only temporarily.
Hi, its great Water Dispersant/Displacer, hence WD.
I've been told by mechanics that they regard it as a dry lubricant, great to get something stuck moving again, but no long term advantages compared to good oil or grease and regular maintenance.
Jantje:
For instance why does my sliding door slide lots easier when I spray "the hard to reach nearly fully enclosed wheels" with WD40?
Collected dirt/dust that the WD cleans out.
Also don't oil bicycle chains except to soak them overnight once a year if you haven't stretched it past usefulness by then. For everyday or weekly cleaning, run the chain through a kerosene soaked rag. Oil on a chain catches dirt and grit that wears the bearings. This from someone that did stretch chains and snap teeth off cogs from a year or less of constant wear.
And that is, indeed, one of the things it is good for.
I had a car with a sticky seatbelt latch. OK when the weather was really dry, but bad when it was damp. Which was a lot of the time, 30 minutes south of Seattle, WA. Sniffing it told me it was some kind of cola spilled in it, probably multiple times.
So I hosed it out with 409 (water based cleaner/degreaser) on stream to wash it out, then WD40 to rinse out all the water. No oil added. Worked great.
GoForSmoke:
Also don't oil bicycle chains except to soak them overnight once a year if you haven't stretched it past usefulness by then. For everyday or weekly cleaning, run the chain through a kerosene soaked rag. Oil on a chain catches dirt and grit that wears the bearings. This from someone that did stretch chains and snap teeth off cogs from a year or less of constant wear.
A couple times a year, I'll take the chain off, give it a thorough de-greasing and cleaning and and also clean what I can off the sprockets by working a rag between them. Just finished a fairly complete tear-down plus replaced the tires so it looks almost factory-new ATM