The oxidation stability experiment and TGA were carried out to estimate the life time of polyolester oil, Turbo Oil 2380 (STD) and Jet Oil 291 (HTS). According to TGA resutls analyzed under air atmosphere, the life time of STD oil showed 127, 63, 33, 14, and 6 min at 175, 189, 204, 218, 232 ℃, respectively. Also, HTS oil showed the life time of 178, 78, 48, 12 and 8 min at 175, 189, 204, 218, 232 ℃, respectively. Thus, the life of HTS oil was longer than that of STD oil. As the results of oxidation stability experiment of STD oil analyzed FED-STD-791 Method 5380, the life time according to viscosity results (limit of life : 15% change) showed 463, 33.5 and 14.1 hr at the temperature of 175, 204 and 218 ℃, respectively. And the life time according to TAN results (limit of life : 2.0 change) showed 1346, 54.9 and 12.4 hr at the temperature of 175, 204 and 218 ℃, respectively. Weight change of metal specimens were less than ±0.2mg/cm(2) and the color of SUS 304 and AMS 4700A were changed after oxidation experiment. The color change was caused by accumulation of oily oxide.