Transformers have always used mineral oil as a liquid dielectric, and scientists have noted its harmful effects on human health and the environment. For more than two years, these vegetable oils have been positioned as real substitutes for mineral oils in view of their excellent physical, chemical and thermal properties. However, being oils sometimes intended for human consumption, such as sunflower oil, corn oil, olive oil, rapeseed oil, soya oil, rice bran oil, coconut oil, palm oil and many others, it is imperative to orientate the use of these oils towards the needs of the population. It is imperative to direct their use to natural non-edible esters in order to avoid a food shortage. Work is being done in this direction, but these are not yet fully determined in terms of their physico-thermal properties as in mineral and other edible oils. This work is a contribution to the determination and analysis of the physico-thermal properties of palm kernel and castor oil methyl esters (PKOME and COME) at variable temperatures. A comparison of the behavioural results with mineral oil (MO) widely used in processors shows a similar trend. Also, the values obtained by extrapolation at room temperature are compared to the values found in the literature concerning: relative density, we have a relative error of 3.47% for PKOME, 0.10% for COME, for kinematic viscosity we have a relative error of 8% for PKOME and 1.46% for COME. The second order polynomial correlations established from the measurements have a coefficient of determination close to 1. The values obtained from these correlations are in accordance with the expectations of ASTM D 1217 for relative density, ISO 3104 for kinematic viscosity, ASTM D 7896 for thermal conductivity and the adiabatic calorimetry method for specific heat.