[Arran]

Mineral oil is way to thick, and viscous, so much so that I have used it to lubricate a bicycle chain. I would not use it to clean anything, it's more then likely that it will leave some sort of sticky residue. As to what to use to clean a Philco dial I would ask what year and what model? On the 1936-38 sets many will wash away with water, on a 1930-32 set it will not. On my Philco 60L the dial was not a wash away scale, nor was the 3118 one which is a 1934 or 35 set, but I can't speak for all models. I would think something like naptha or kerosene might be alternative to mineral spirits, but not mineral oil.
Regards
Arran