What kind of oil lube for a vintage penny scale? Answered

sewing machine oil is good, it doesn't go gummy with age. Also, I've found the oil used for paper shredders is pretty good too

A very good instrument oil can be made as follows: To 2 ounces of Mineral Oil (yes, the kind you can get at any drugstore-pharmacy), add 4 to 5 drops of Mineral Spirits (a.k.a. Stoddard's Solvent). Apply liberally, then remove all that you can with a paper towel or soft absorbent cloth. Also, the operation and accuracy of your scale depends on either or both, a spring or springs, and (triangular) knife edges that form the fulcrum point or points. Make sure these are in place, rust free, clean, and not too badly worn or broken. Good luck!

I dunno. 3-in-One(r) oil would probably work.

https://en.wikipedia.org/wiki/3-In-One_Oil

WD-40(r) would likely work also.

https://en.wikipedia.org/wiki/WD-40

I don't know if those particular brands exist in your part of the English-speaking World, which part of why I dislike recommending brand names. If those brands are not available in your part of the World, then you have to figure out what substitutes do exist, and the names used to refer to them.

Probably, any low-viscosity, petroleum-based oil would work.

It might also depend on which dispensing method you like better, e.g. drop by drop, or aerosol spray through a plastic straw. Which is which, you can sort of infer from the pictures, and words, in the Wiki articles linked above.