It has been recognized that the friction coefficient decreases with decreasing viscosity of lubricant oil in lubrication. In general, as the viscosity of the lubricant decreases, the wear rate increases due to a decrease of load-carrying capacity of the lubricant. It has been proposed that nano particles in oil decrease the friction coefficient and wear rate. The purpose of this study is to apply oil, which has lower viscosity and is mixed with nano particles, to the compressor used in a refrigerator to decrease the friction coefficient with the same or superior load-carrying capacity. Mineral oil of 8 mm(2)/s was used and mixed with fullerene nanoparticles of 0.1 vol%. Friction coefficient was evaluated by a disk-on-disk tribo-tester. As a result, the friction coefficient of the nano-oil decreased by 90% in comparison with raw oil. These results lead us to the conclusion that nano-oil can contribute to improving the efficiency and reliability of the compressor. (C) 2009 Elsevier B.V. All rights reserved.