It's not bad at cleaning kitchen grease off range hoods if you've got stainless steel. And you get a great "manly" scent.

I used to use it as a carburettor aide for rarely used lawnmowers to kick start them into life but this is probably bad for the engine. There are real products for this.

Penetrative oil for mildly rusted on screws and bolts.

And.. a really bad chain lube, or hinge de-squeeler. Basically these things deserve proper lube molybdenum/disulphide stuff. You're depending on the graphite (I think) in wd40 to do the job before the solvent strips all the real lube out.

You made me laugh with the manly scent part.

As a kid, I thought washing my hands with "swarfega" is what grown ups just did. I truly do have very happy memories of the smell. And clean hot machine oil and electronics has a fine scent all of its own.

It's a solvent and a penetrating oil. It works for cleaning, getting something unstuck, or making sure something has no water on it (the "WD" is for "Water Displacement"). But it evaporates quickly and that's not good for anything you want to stay lubricated. It's okay for getting a rusty bolt moving because it's thin and easily gets where something thicker would not. It's not suitable for machinery that needs oil permanently on it. Also not good for locks, since it tends to gum them up.

In general if you need to lubricate anything important, you should look into what the official documents recommend. The right lubricant varies a lot depending on the application. Some stuff uses thin oils. Some uses sticky oils. Some wants grease. The right thing to use depends on things like manufacturing tolerances, the presence of oiling systems and the operating environment, so best to just check the manual.

I have used WD40 plenty of times to clean and lubricant rusty locks, in my opinion it works better then most other lubricants out there. And No my lock did not had manual about right lubricant.

Many years ago I tried Super Lube® Multi-Purpose Synthetic Lubricant for locks exposed to weather 24x7, including one that spends 3 months a year buried in snow, and it is far superior to WD-40, as in multiple years of smooth operation without further maintenance. I might clean a lock with WD-40, but i am always going to lubricate outdoor locks with Super Lube. I have no idea if it works so well because of the base oils or the teflon additive or the combination, but it is really good stuff. This summer I used it to rehab my rusted grindy 38 year old Swing-A-Way can opener, which is now butter smooth, and to fix a seized outdoor A/C condenser fan. For both I had no direct access to the bearings and had to flood Super Lube down the shafts. Worked amazingly well.

you're using it to help break a stiff or rusty lock, but it's not lubricating anything.

Water and humidity displacer, and a penetrating oil to help unlock rusted/stuck nuts and bolts.

Especially the second thing depends I guess on capillary properties, which other lubricants (e.g. silicon oil) don't necessarily have?

AFAIK, It's what you use before lubricating things, if the thing in question has not seen a lubricant in a long time. Once the movable parts are moving again, other lubricants are better.

It's pretty good to start things moving, IMHO. Bit of WD40 at first then apply a proper lubricating oil.

I've also used it on bike chains, to clean off a lot of the old nasty before reapplication of a purpose-created lube.

> I've asked this question to many people and they never had a good response.

One might suggest:

A) Reading what it says on the tin can what it is for

B) Consulting its Wikipedia page, which states in the first sentence that it is a https://en.wikipedia.org/wiki/Penetrating_oil, and that article further explains what those are good at, and what not.

As the article states in the first paragraphs—nudge, nudge—WD stands for ‘water displacement’ and was formulated in the aeronautics industry for the prevention of rust.

I use it to winterize my motorcycle in winter months giving the metal parts a thin film of WD-40 (being careful to avoid the brake calipers and rotor).