Optimus Transformer Oil (Inhibited) is a series of products blended using highly refinedmineral oil and a selected antioxidant package. It is designed for insulating and coolingtransformers, oil-immersed switch-gear and other electrical insulating applications.There are four grades, 10, 25, 40 and 45, which are selected on the basis of their low-temperatureperformance. None of the grades contain harmful polychlorinated biphenyls(PCBs).