This document provides 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@ de-energized tap changers (DETCs)@ load tap changers (LTCs) (where applicable)@ and coil re-clamping. The goal of this guide is to assist the user in extending the useful life of a transformer Purpose The purpose of this guide is to provide guidelines for evaluation and reconditioning of transformers. This guide should prove helpful to users who do have evaluation and reconditioning programs in place@ and who may not be aware of other activities and processes that are available. The guide is intended as a comprehensive document to aid users in selecting the proper approaches to upgrading@ reconditioning@ refurbishing@ or other activities in extending the useful life of a transformer