ASTM D4742 Oxidation Stability of Gasoline Automotive Engine Oils by Thin-Film Oxygen Uptake (TFOUT)
Engine oils must often operate in the presence of compounds that may increase the rate of degradation and sludge formation. These compounds include water (from condensation, leakage or other sources), nitrated/oxidized fuel components (from leakage of other automotive systems) and metal naphthenates (from anti-corrosion and detergent additives). This test determines the relative stability of engine oils in the presence of these contaminants.
The sample engine oil is placed in a glass container and water, nitrated/oxidized fuel components and 5 metal naphthanates are added. The container is pressurized with oxygen and heated. The pressure is monitored until a sharp decrease is observed indicating oil break down. Reported is the oxidation induction time (from test onset until sharp pressure drop).