The purpose of this guide is to further oil conservation by providing detailed procedures for reclaiming used mineral insulating oils by chemical and mechanical means, making them suitable for reuse as insulating fluids. The guide describes the essential properties required for reuse in each class of equipment and the recommended test methods. The purpose of ANSI/IEEE C57.106-1977 [24]1 is to aid the operator of the electric power equipment to evaluate the serviceability of new, unused transformer oil contained in new equipment, or as received from the refiner for filling new equipment. The recommendations and tests in ANSI/IEEE C57.106-1977 [24] are intended also to provide the operator with good estimates of the continued reliability of the oil in service in equipment and guidance for the reconditioning of oil by mechanical means. These estimates in turn suggest minimum property limits for restoring used oils to as near theft original condition as possible utilizing current techniques.