Reducing the toxicity of exhaust gases from internal combustion engines remains an urgent task both now and in the future, despite the widespread development of electric vehicles. The three-way catalyst (TWC) system for reducing the toxicity of gasoline engines is well known. One of the characteristics of the catalytic unit used in after treatment systems is the oxygen storage tank (OSC). OSC can be measured in various ways. The technological oxygen storage capacity is a parameter measured by an electronic control unit on a car by comparing signals from oxygen sensors installed on the hot end. The engine method is an investigative method for obtaining the full oxygen content on the surface of the neutralizer in a wide range of temperatures and calculating OSC values. This article presents a comparison of the OSC values obtained by these different methods. In order to establish a relationship between the true oxygen capacity measured during coating development and block production and the process capacity continuously measured during calibration, certification preparation and block aging, it is necessary to supplement the existing catalyst model. For the first time, the possibility of correlation using a scaling factor between OSC values was established in the practice of system development and calibration.