Abstract A new scuffing parameter for gears lubricated with mineral base oils is developed, proposing the existence of gear mass temperatures which are critical for each lubricant (viscosity grade). The introduction of the total cycle of the gear for mass temperatures calculation is supported by a theoretical background that was clearly established without empirical formulation and without any geometrical gear specificity which provides consistent physical support to the proposed scuffing parameter. The oil dynamic viscosity at the critical mass temperatures is constant, allowing the prediction of critical temperatures for other viscosity grades of the mineral gear oils without the need of additional scuffing tests.