Transition from Euro-4 to Euro-6 implies stricter requirements for emissions of hydrocarbons, including 2.2 - 3.4 times stricter requirements for methane, depending on the type of engine, regulated exhaust component and normalized test cycle (Table 1). For example, for CH4 it corresponds to emission reduction from 1.1 g/kWh (ETC - cycle) to 0.5 g/kWh during transition from Euro-4 to Euro-6. The task of satisfaction to the standards for nitrogen oxides is even more difficult. In accordance with the norms for complying with future requirements quoted in the table 1, the toxicity levels caused by nitrogen oxides should be reduced by more than 8 times during transition from Euro-4 to Euro-6. Standard values for other toxic components are significantly reduced too. It is necessary to take into account the effects of inevitable aging, which affects components of the system. As a result, the initial levels of treatment should be set with a significant (20-30%) margin.