AbstractThe long‐term thermo‐oxidative stability of lubricants and greases is a prerequisite to meet today's ‘stay in grade’ and extended drain interval requirements. To achieve this goal, there is a need for a better understanding of thermo‐oxidative lubricant degradation and of how antioxidants can affect this process. In this paper a two‐stage degradation model is discussed. Primary degradation leads to the formation of very reactive species such as radicals and peroxides. These are the precursors for generating secondary degradation products, such as oligomers, sludge, or deposits. By applying the theory of reaction kinetics and the Arrhenius law, quantitative correlations may be derived between oxidation induction time (OIT) and temperature, and between OIT and antioxidant treat level. Pressurised differential scanning calorimetry (PDSC) data confirm these theoretical findings and demonstrate the benefit of the addition of aminic antioxidants in comparison with high‐molecular‐weight hindered phenol