Development of a new oxidation stability test method for lubricating oils using high-pressure differential scanning calorimetry

There is an industry-wide need for a rapid oxidation bench test that can be used to establish the oxidation stability of engine oils, greases, transmission and hydraulic fluids, turbine oils and vegetable oils. The oxidation stability of lubricants as estimated by high-pressure differential scanning calorimeter (PDSC) has long been of interest to the thermal science community. A group of industrial lubricating oils were used to establish a relationship between certain standard variables and oxidation induction times (OITs) by PDSC. The variables studied were temperature, pressure, heating rate, sample mass, sample pan types, soluble catalyst concentration and gas flow rate. Several oxidation induction time methods were developed to rank a series of lubricating oils. These results correlated well with an oxidation stability test (ASTM D943) used widely to characterize industrial oils. The new method is rapid, employs a soluble metal catalyst and requires only microliter samples for testing with good precision.