This guide includes guidelines for the following: insulating oil maintenance and diagnostics, oil reclamation, testing methods for the determination of remaining insulation (paper) life, and upgrades of auxiliary equipment such as bushings, gauges, deenergized tap changers (DETCs), load tap changers (LTCs) (where applicable), and coil reclamping. The goal of this guide is to assist the user in extending the useful life of a transformer. Up to now, there have been no formal guidelines for evaluation and reconditioning of transformers. Users that do have evaluation and reconditioning programs may have only specific practices they use, but may not be aware of other activities and processes that are available to them. The purpose of this guide is to develop a comprehensive document that will aid users in selecting the proper direction for their unique needs. New IEEE Standard - Superseded. This guide includes guidelines for following: insulating oil maintenance and diagnostics, oil reclamation, testing methods for the determination of remaining insulation (paper) life, and upgrades of auxiliary equipment such as bushings, gauges, deenergized tap changers (DETCs), on load tap changers (LTCs) (where applicable), and coil reclamping. The goal of this guide is to assist the user in extending the useful life of a transformer.