Lots of solvent in penetrating oil.I used to keep Kroil in a pump oiler. Not any more! The check ball in the oiler would stick and not pump. I'd have to take it apart and free it up. I didn't need to use if for a couple of years, and the next time I did, it wouldn't pump. The check ball had rusted to the cylinder, and the whole inside of the unit was rusty.
It was an inexpensive unit from the local NAPA store, but oil shouldn't attack steel!