Naphthenic process oils are made by blending one or more naphthenic vacuum gas oils in one or more viscosity ranges with a high CA content ethylene cracker bottoms, slurry oil, heavy cycle oil or light cycle oil feedstock to provide at least one blended oil, and hydrotreating the at least one blended oil to provide an enhanced CA content naphthenic process oil. The order of the vacuum distillation and blending steps may be reversed.