<p>To prevent global warming, spread of electric vehicles is progressing globally. In case of electric vehicles, it becomes impossible for car heating to use waste heat from engine operation, so heating function is also required for car air-conditioning system. Dual use of heating and cooling forces wider range of temperature and longer operation of compressor, which suggests severer lubrication condition. In the compressor of car air-conditioners, various bearings and materials are lubricated in a mixture of refrigeration oil and refrigerant. Longer fatigue life of bearing becomes further expected in such a severer condition. There are two major factors of fatigue life: base oil and additives in lubricants. In terms of the base oil, it is assumed that higher viscosity can form thicker oil film and obtain longer fatigue life. On the other hand, in terms of the additives such as anti-wear agents that react with metal surfaces, there are only a few examples of studies about fatigue life conducted under the mixture conditions of refrigeration oil and refrigerant. Still unknown about the effect of additives in refrigerant circumstance. In this study, the effect of phosphorous type anti-wear agents formulated in refrigeration oils was evaluated. It was found that phosphite esters in refrigeration oils contributes fatigue life extension in refrigerant circumstance.</p>