Mechanical degradation of polymeric additives in lubricants has been a topic of extensive study since complex formulations were introduced to reduce the temperature dependence of viscosity. Many devices, which are able to shear polymers, have been tested for their abilities to simulate the degradation observed in engines and other lubricated systems. Conclusions drawn from these studies are often ambiguous as they depend on the test protocol and method of data analysis. In this work, a simple expression based on probabilistic arguments is used to describe kinematic viscosity data from a variety of degradation simulators. This expression provides a method of comparing extent and rate of degradation for different simulators.