Hydrocarbon fluids are provided which have ASTM D-86 boiling point ranges within 235.degree. C. to 400.degree. C. and a naphthenic content greater than 60%, the naphthenics containing polycyclic materials, the fluids preferably have an aromatic content below 2% and an aniline point below 100.degree. C. The fluids are particularly useful solvents for printing inks, drilling fluids, metal working fluids and as silicone extenders.