Mineral oil is a very old term. There was a time when oils and greases from from crude oil were a new thing. At the time, greases and oils typically came from animal fat.
Such as bear grease.
This product was a quack medicine sold to men who where either losing their hair, or had gone bald and wanted hair to grow back. Bears are very hairy, and quacks convinced many that rubbing bear grease on a man's head will make the hair grow. The logic is irrefutable: bears are hairy, therefore the application of bear grease with make a man's heads hairy. Satisfaction guaranteed.
It did not work as intended, but it did sell well.
Mineral oil is just something that came out of a distillation tower and the viscosity of which is thin enough to make a room temperature lubrication. Plain mineral oil is just oil, nothing else. If oxygen migration blocking additives are added, then the oil will work as a rust preventative till the oil evaporates. Additives are what makes the difference between plain mineral oil and more advanced lubricants. That and the base oil, whether natural or synthetic.
I remember from chemistry class:
"Like dissolves like". If the crud is organic, then oil will dissolve it. Some organic liquids, such as mineral spirits, are more aggressive solvents. Brake cleaner is a very aggressive cleaner,
according to the MSDS, it is mostly acetone. I was holding a gun part covered in dried cosomoline and sprayed brake cleaner on it. The nitrile glove on my hand ripped and I got a chemical burn from that brake cleaner. I am sure the velocity and pressure of the spray can injected brake cleaner into my skin, and my skin peeled for over a year. The body does not have the ability to neutralize modern chemicals. I have used kerosene to dissolve the tar from pulled military bullets. It worked, took a while, but it worked.
Primer deposits contain heavy metals, such as barium, and barium oxide. Both of
which dissolve in water.
Barium sulfate requires an acid to dissolve.
