By oil
Nyoil as Grant Cunningham so knowledgeably states in his article is a non-staining substitute for ATF as a Gun lube. With all respect due to other posters, I've studied this topic long and hard as a former chemistry professor. ATF and Nyoil are both chemically and physically sperm whale oil substitutes to a very great degree.
As fine gun experts such as Ned Roberts inform us, gunsmiths and fine mechanics long knew, even before the 1800s, that sperm whale oil was a highly superior lubricant, and today so are ATF and nyoil. They can work for clocks AND firearms. Today, we have the full analytical specs to tell us what we need to know. While these products may not be the better choices for slide lubrication on a semi-auto pistol or a shotgun, or on a revolver's rebound slide, where a light grease is required, they are excellent oils for many other pivoting, rotating, or lightly sliding points. Many gun oils are not anywhere near as good lubes or corrosion-inhibitors as quality ATF or non-toxic Nyoil. (And please don't tell me you won't use anything with "ATF" in the name -don't make us look like jackasses!). Read Cunningham's article, which is the best I've read in the firearms literature on gun lubes, and don't buy -or swallow- snake oil!!!! Send the money you save to your state firearms organization or the NRA.