The present work investigates the storage and oxidation stabilities of 100% biodiesel (B100) derived from waste cooking oil. Physical properties and chemical composition of B100, including viscosity, density, peroxide value, heat of combustion, acid number, and phase behavior, were measured. The analysis showed that this B100 contains over 60% unsaturated esters. The long-term storage stability was studied based on ASTM D4625 which simulates up to two years storage by holding samples at 43 degrees C. Modified ASTM D5304 and D2274 tests were conducted to investigate oxidation processes of B100. An extended ASTM D2274 method was also employed to investigate the influence of oxidation time on stability. The influence of long-term storage and oxidation reactions on physicochemical properties and phase behavior was investigated using ASTM methods. The existence of three stages of B100 oxidation was identified based on the property changes after the modified ASTM D5304 and D2274 tests. Published by Elsevier Ltd.