In the framework of Transformation 2.0 moonshots, one of the key goals is to achieve Net Zero Emission through the moonshots-green enabling transmission initiative, as part of PLN’s effort to deliver environmentally friendly technologies and energy. One such effort is the use of natural ester oil as insulating oil in transformers, due to its biodegradable nature. In accordance with IEC 62975:2021, natural ester oil offers the potential to enhance sustainability by reducing dependence on fossil-based resources. To support the implementation of natural ester oil in transformers, research related to its performance is essential. The objective of this study is to analyze the comparison of characteristics between mineral oil and natural ester in distribution transformers and to evaluate the comparative impact of natural ester and mineral oil on insulating paper. The method used in this research is oil testing and paper testing on a laboratory scale and on distribution transformers. Based on the results of testing on oil samples conducted, natural ester oil has higher characteristics in the breakdown voltage parameters in February of 45 kV; July of 56 kV and November of 71 kV, water content in February of 187.56 mg/kg; July of 45.13 mg/kg and November of 105.13 mg/kg, viscosity in February of 33.38 cSt; July of 33.38 cSt and November of 32.61 cSt, acidity, dielectric dissipation factor (DDF) in February of 0.0580; July of 0.0298 and November of 0.04923 and flash point in February of 236.5°C and November of 232.5°C. In the results of laboratory testing, the DP value of insulating paper immersed in natural ester oil was 1417.3; 567.75; 459.66 and 448.61, while the mineral oil-immersed insulation paper had values of 1482.16, 466.57, 441.73, and 429.11. This indicates that the decrease in the DP value of natural ester oil is slower than that of mineral oil-immersed insulation paper. Thermal aging accelerated at 150℃ in mineral oil-immersed kraft paper has values of 100%, 72%, 53% and 34% while immersed in ester oil has values of 100%, 92%, 90%, 62%. The decrease in tensile strength retention value is more significant in mineral oil-immersed kraft paper compared to ester oil. The results show that natural ester oil is more effective in maintaining the integrity of transformer insulation paper from thermal aging compared to mineral oil.