Increasingly engineers are seeking to verify HDPE Polyethylene geomembrane durability characteristics by testing oxidative induction time before and after accelerated ageing of the material. Typically, 90 days of ageing in air is required in an oven at 85 °C which requires a significant time for material specification conformance testing prior to installation. This paper reports on studies undertaken to refine the high-pressure oxidative induction time test process to allow this material durability indicator to be characterized in a shorter period. The study included assesses the response of different HDPE material formulations and skin conditions to the test procedure. Different sample preparation procedures were also examined. A proposed alternative durability test process is proposed for consideration.