IEC 60296:2020 provides specifications and test methods for unused and recycled mineral insulating oils. It applies to mineral oil delivered according to the contractual agreement, intended for use in transformers, switchgear and similar electrical equipment in which oil is required for insulation and heat transfer. Both unused oil and recycled oil under the scope of this document have not been used in, nor been in contact with electrical equipment or other equipment not required for manufacture, storage or transport. Unused oils are obtained by refining, modifying and/or blending of petroleum products and other hydrocarbons from virgin feedstock. Recycled oils are produced from oils previously used as mineral insulating oils in electrical equipment that have been subjected to re-refining or reclaiming (regeneration) by processes employed offsite. Such oils will have originally been supplied in compliance with a recognized unused mineral insulating oil specification. This document does not differentiate between the methods used to recycle mineral insulating oil. Oils treated on-site (see IEC 60422) are not within the scope of this document. Oils with and without additives are both within the scope of this document. This document does not apply to mineral insulating oils used as impregnating medium in cables or capacitors. This fifth edition cancels and replaces the fourth edition published in 2012. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: – This International Standard is applicable to specifications and test methods for unused and recycled mineral insulating oils in the delivered state. – Within the transformer insulating oils, two groups, Type A and Type B, are defined, based on their performance. – A new method for stray gassing under thermo-oxidative stress of mineral insulating oils, which has been tested in a joint round robin test (RRT) between CIGRE D1 and IEC technical committee 10, has been included.