Lubrication -- is fine machine oil "better"?

Skrew

So there is always a debate on gun forums over if lubricants marked for firearms are better then motor oil or cheaper automotive lubricants.

I'm curious if anyone here has any hard information on the differences and what is better?

Danger

Such lubricants, whether for firearms or small appliances, are of very "fine texture". That's not a proper term, but it conveys what I mean. There's low viscosity, and thus very small droplet size. An extreme example is WD40. You would be amazed at how many people don't realize that it's oil. A lot of them think that it's silicone or Teflon or some other exotic substance.
By the bye, don't ever use any type of oil in a lock, including WD40. (Free advice from a professional locksmith.)
Although I'm not sure, I suppose that gun oils might also contain anti-corrosion compounds in addition to that natural quality of petroleum products.

pantaz

"Better" is relative. I imagine the debates you speak of relate to the use of motor oil in firearms, rather than the other way 'round -- A lubricant designed for firearms isn't going to work very well in a car's engine.

If nothing else is available, motor oil would be preferable to leaving the mechanism dry. However, motor oil isn't designed to sit on a static surface as a corrosion preventative, as many gun oils are. Motor oils typically also have much greater viscosity preventing them from easily wicking into all the tight little spaces. One also has to consider the type of lubrication (oil, grease, dry film). A lubrication engineer could expand on this whole topic considerably.

Jobrag

"By the bye, don't ever use any type of oil in a lock, including WD40. (Free advice from a professional locksmith.)"

I'm not doubting that it's good advice, but why?

Mech_Engineer

In my experience dry lubricants like graphite powder don't collect dirt and grime, where as oil such as WD-40 will collect these things and over time you'll actually be worse off.

turbo

WD-40 will strip other lubricants out of your firearm. Not good. It is a really good solvent, but not a good lubricant for firearms.

Years back, a whole generation of vets were returning from VietNam with a devotion to graphite grease (Gunslick, in particular). My father bought a Remington 742 really cheap that way. Deer-hunting in very cold weather was a strain on graphite greased actions, since it thickened and caused jams. Tear down the rifle, clean it and re-lubricate with a light oil -sewing machine oil is fine - and you're good to go.

Danger

Quite right. The collected dust turns into mud, and eventually into cement. It's particularly nasty if the lock is installed upside-down, which occurs with disturbing regularity. Graphite powder is the proper lubricant (not the graphite grease that Turbo mentioned). If oil gets in, soak the thing in alcohol (preferably disassembled), then lube it with graphite after it's dry. Silicone or Teflon sprays are acceptable as well, but they're generally too expensive to bother with. If you're wondering about where to get graphite, just hit your local auto parts store and ask for a tube of speedometer cable lube. A 100 year supply should cost about $3.00, and there's no expiry date. (I used the stuff in every lock that I ever worked on in my 17-year career, and went through 2 tubes in addition to the "puffer gun" that came with my college course kit. Just before I retired I bought a 1/2 kg can, and have no idea what to do with it.)
I should specify here that I'm referring to the pin cells of locks, where the key goes in. It's okay to use oil on the bolts.