The application of nanolubricant enhanced the performance of the automotive air conditioning (AAC) system. The performance of electrically driven compressors in AAC systems (AAC-EDC) can be greatly enhanced by the stability of nanolubricants. Thus, the stability of TiO2/POE and SiO2/POE mono nanolubricants at temperatures up to 100 °C and volume concentrations ranging from 0.01 to 0.1% is examined in this study. Using a two-step preparation method, TiO2 and SiO2 nanoparticles were dispersed into the Polyol-ester (POE) base lubricant. Two approaches are used in the stability evaluation of the nanolubricant: qualitative and quantitative. The qualitative approach uses visual observation. In contrast, the quantitative method is used Ultraviolet–visible (UV–Vis) spectroscopy and zeta potential evaluation. According to the visual observation, SiO2/POE nanolubricants exhibited the best stability, followed by TiO2/POE nanolubricants. Meanwhile, from the UV–Vis spectroscopy evaluation, mono TiO2/POE sustained the concentration ratio by more than 90% with a sedimentation time of up to 30 days. The zeta potential of the TiO2/POE and SiO2/POE mono nanolubricants was higher than 60 mV, indicating exceptional stability. It can be stated that the nanolubricants from this study have outstanding stability conditions and can be used further in the application of the AAC-EDC system.