Proposed standard ASTM WK21616, Test Method for Oxidation Induction Time of Natural Ester Insulating Fluids by Regular Differential Scanning Calorimetry (DSC) will provide electrical power industry with straightforward test for oxidation stability of natural esters. Described DSC oxidation induction time method takes 2–3 hr, is direct oxidation measurement requiring minimal sample size, and does not use hazardous laboratory chemicals that require disposal.