What type of fluid can be used to top off a wecosol transformer?

Wecosol Fluid is no longer manufactured or available. It was a fire resistant insulating oil manufactured in the 1980s by Westinghouse. It was made from a mixture of chlorinated solvents and mineral oils. Wecosol Fluid was a very good heat transfer fluid, so a low viscosity hydrocarbon should be used for retrofill, such as Alpha-1 Fluid (PAO based) or a synthetic ester such as Midel 7131 or Cargill Envirotemp 200. Silicone fluid should not be used. .