The application of carbon dioxide as the refrigerant in vehicle air conditioning requires the development of a suitable lubricant for the quickly rotating compressor. The phase behavior of different synthetic lubricants with carbon dioxide forms the basis for developing a CO2- cooling circuit. Furthermore, the influence of carbon dioxide upon the viscosity of the oil is essential for evaluating a lubricant. These data of the binary mixtures have been measured at temperatures between 5 and 100 degreesC under pressures of up to 150 bar. The qualitative observation of phase behavior took place in a high-pressure view cell, whose complete content is monitored: The phase equilibria have been determined in an autoclave based on a static-analytical method. The viscosity of the lubricant which is saturated with carbon dioxide has been measured with an integrated quartz viscosimeter. The phase behavior of oils with carbon dioxide can be divided into three different types: binary systems with closed miscibility gaps, systems with open miscibility gaps, and systems that shaw barotropic phenomena. Oils that show barotropic behavior in contact with compressed carbon dioxide are not recommended as lubricants. Oils with complete or limited miscibility with carbon dioxide may be used. The knowledge of phase behavior and the resulting viscosity of gas-saturated lubricants allow one to evaluate the applicability of lubricants in car-climatization systems.