Recommendations are made regarding oil tests and evaluation procedures; methods of reconditioning and reclaiming conventional petroleum (mineral) dielectric oils; the levels at which these methods become necessary; and the routines for restoring oxidation resistance, where required, by the addition of inhibitors. The intent is to assist the power equipment operator in evaluating the serviceability of oil received in equipment, oil as received from the refiner for filling new equipment at the installation site, and oil as processed into such equipment; and to assist the operator in maintaining his oil in serviceable condition. The mineral oil covered is used in transformers, switchgear, reactors, and current breakers.

The reliable performance of oil in an insulation system depends upon certain basic oil characteristics which can affect overall apparatus characteristics. Such oil characteristics are integral parts of the equipment design for which the manufacturer has final responsibility. The reliable operation of the equipment in service for which the electric power producer has final responsibility also depends on maintaining certain basic oil characteristics. Adherence to the recommended oil characteristics will assist in obtaining the desired equipment characteristics. Other tests or verification of the integrity of the insulation system are often necessary and required.