The purpose of this standard is to establish the characteristics that must be met by new mineral insulating oils used in transformers and switches. These oils are obtained by refining and distilling crude oil. This standard also establishes the test methods that must be used. The standard is applicable to new mineral oils, inhibited or uninhibited, used in transformers and switches, and, in general, in equipment in which mineral oil, in addition to being an insulator, is used as a cooling fluid. The standard is not applicable to insulating mineral oils used as impregnants in cables and capacitors or to dielectric liquids based on synthetic hydrocarbons. NOTE- Mineral oils that meet the requirements of this standard, belonging to the same class and that also do not contain additives, are generally compatible with each other, and can be mixed in any proportion. This is not always applicable to mineral oils that contain additives; In these cases, when the user wants to mix these oils, they must check whether the mixture meets the requirements of this standard. The difficulty of knowing in practice the formulation of a mineral oil makes it advisable to carry out a compatibility test prior to using the mixture.