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There are many different kinds of "honing oils" to suit different needs. It is important to use the appropriate solution for the job. In the case of knife sharpening, motor oil is too thick or "heavy" and can over-lubricate or clog a sharpening stone, whereas WD-40 is too "light" an oil and will not carry the metal filings plus stone dust (collectively known as "swarf") away from the stone, and clog it. Not using any oil at all will also clog or "glaze" the stone, again reducing its cutting power.[5] Historically sperm whale oil, Neatsfoot oil, and other animal fats were popular.
It wouldn't surprise me if a hundred plus year old Arkansas stone had seen some of all of the above. I've got a few that have been used with various motor oils, WD-40, Crisco, bacon fat, spit (with and without tobacco juice), corn and vegetable oil.