Billy
I got the idea of lighter fluid as a quick easy way to buy Naphtha from "Those Fantastic Featherweights" By David R. McGallum. Other chemicals are very destructful to japan (Shellac) finishes. Alcohol is the solvent for shellac and will distroy the finish of the pre 1960 machines on contact.
My 7th and 8th grade wood shops used shellac as a finish and that is where I started to use naphtha.
You will enjoy your Singer 500. My wife and I purchased a Singer 501 new in 1961 and it has never been in the shop. She has done all of the maintenance herself and she still uses it.
Thanks for your input, nice to have a sewing machine professional in the group.
Ken