Testing FOR oil? Part of the issue I think is the different definition of “oil” The PG and VG in
vape juice is “oily” but it’s not oil. While some places refer to anything oily as oil this is not the definition used in the U.S. (or any oil producing country afaik) oil is the way hydrocarbons bond together. They are not all “oily” (some are tarry some are watery) and there are things that are “oily” that are not oil. In vape
juice VG (and to a lesser extent) PG are “oily”. There CAN be oil as well. Cinnamon oil is a famous one. Oils have long term problems when vaped. There is such a thing as “water soluble oil” which is sort of a contradiction in terms. I’m not sure how that is accomplished. Possibly with a surficant which just breaks them up into tiny pieces.