The viscosity, solubility, and density of several two- and three-phase lubricants were determined experimentally in a temperature range of 80 F to 200 F and a pressure range of 50 psia to 600 psia. Equations were found which would accurately describe the viscosity and density of these lubricants at other temperatures and pressures. Micro-size particles of molybdenum disulfide were suspended in petroleum-base oil with absorbed quantities of various gases. Lubricants of 4 weight per cent gas-oil mixtures had viscosity decreases of up to 60% relative to the oil viscosity, while the oil density remained virtually unchanged.Contributed by the ASLE Technical Committee on Properties of Lubricants and presented at the Annual Meeting of the American Society of Lubrication Engineers held in Cincinnati, Ohio, April 1960.