I haven't looked at the MSDS/SDS for it, but it wouldn't surprise me at all if singer sewing machine oil was just like Hoppe's #9 oil and contains nothing more than white mineral oil. There's nothing wrong with that from my perspective and I would much rather have it smeared all over my pillow rather than some of the other toxic garbage people use on their guns, but you can buy the stuff in the pharmacy for a fraction of the price and it will actually be better since it will be USP grade. I don't think keeping a gun under your pillow is very wise, but routine inspections and maintenance would be prudent if you do and irregardless of what you use, so oil evaporating or gumming up shouldn't ever really be a concern.