Transformer and turbine oils must have good physicochemical, antioxidant, anticorrosive, and heat transfer properties. The latter are primarily determined by the thermal conductivity lambda and isobaric heat capacity c'(p). The thermophysical properties of turbine and transformer oils have been relatively completely investigated at low temperatures and atmospheric pressure. However, the experimental values of parameters lambda and c'(p) occasionally differ significantly for the same oils, probably due to their origin and manufacturing technology.