How to thin out oil for firearms?

Kerosene

I don't know, but it is a key ingredient in Ed's Red.

What is PL-M oil?

And what makes you think it is still any good after it is already turning into varnish?

Throw it away and buy some decent new oil!!!!

rc

Seems like an awful lot of trouble to avoid paying $3.50 for a bottle of Hoppes oil.

mix some water in

I have long been trying to use up a quart of PL-S a drop at a time with little success.

I have used it as a blend stock for various Internet Lubricants, mixing it with STP and Lucas to thicken, with Militec 1 because I could not find anything it was good for and read that it was originally a gear oil additive. It is still oil.

If you want to thin your PL-M, consider that automatic transmission fluid is a component of many homebrew lubricants, including Marine Red. And if the Marines use it, it must be good, right?

10w Hydraulic oil, 5w air tool oil. Idk why you would want to thin it. I use 75w-90 marine gear oil on my 1911 slide rails and other high wear areas. Works as good as anything and a quarts lasts a long time.

I would say you're much better off grabbing a quart of synthetic motor, plain hydraulic, or gear oil off the shelf at wal-mart for $5.00 or even a regular CLP than you are playing chemist and re-purposing some mil spec product with unknown specifications by adding a solvent. I would advise against ATF or kerosene or any other harsh products laden with additives or solvents to regularly use on your firearms. That stuff is bad news to get on your skin all the time. (which will happen in a firearms application) Petroleum distillates and solvents can permeate your skin and enter the body in many cases. It is simply not good for your long term health. As shooting enthusiasts we expose ourselves to enough cleaning solvents, vapors, and lead exposure. Why voluntarily add to the risks? I dont see the point of carrying a firearm to defend our lives if we arent protecting ourselves from day to day hazards and health risks. As someone that has had to deal first hand with loved ones dying of cancer mostly due to environmental/occupational exposures it's something always on the back of my mind and I wouldnt wish it on anyone on this forum or in the shooting community. Please think about what you're playing around with on your shooting benches and what the risks are. Guns have been running for hundreds of years with plain lubricating oils that are much less harsh on our bodies to deal with than commercial/automotive fuels and solvents or home brewed concoctions. No gun's slide rails are worth your health.

We used PL-S on our M14s back in the '60s. Used Lubriplate on the bolt roller, and a drop of solvent on the gas piston, but PL-S everywhere else.