Abstract: An electrical insulating oil having both high positive and high negative direct current breakdown voltage values is prepared by catalytically reforming a petroleum naphtha or similar feedstock and then fractionating or otherwise treating the reformed material to produce a highly aromatic oil which boils in the range between about 400.degree. and about 700.degree. F., contains less than about 1.0 weight percent of polar compounds, and includes less than about 2.5 weight percent of aromatic compounds having four or more condensed aromatic rings per molecule. This aromatic oil may be blended with up to about 75 volume percent, based on the total blend, of a low aromatic petroleum fraction which has been hydrogen treated, solvent extracted or acid treated to reduce its aromatics content to a level less than about 20% by weight. The aromatic oil or blend may be hydrogen treated or contacted with an adsorbent to improve further its stability and other properties.

Abstract: Naphthenic solvents and low aromatics mineral spirits are produced simultaneously by blending a hydrocarbon oil boiling in the range between about 100.degree. F. and about 600.degree. F. with an aromatics fraction having an initial boiling point similar to that of the oil to produce a blend containing in excess of about 10 weight percent aromatics, hydrogenating the blend in the presence of a hydrogenation catalyst until aromatics present in the blend have been converted into lower boiling naphthenic compounds, and thereafter fractionating the hydrogenated material to produce a highly naphthenic overhead fraction useful as a solvent and a low aromatics bottom fraction useful as mineral spirits.