An uninhibited electrical insulating oil is prepared by blending a severely hydrotreated naphthenic distillate base oil having a viscosity of from about 50 to about 80 SSU at 38.degree. C. and an aniline point from about 63.degree. to about 84.degree. C. with a solvent extracted, non-hydrogenated paraffinic distillate having at least 9.0 wt. % aromatic content.