Studies on the oxidation of diesel particulates characteristically showed that the particle number concentration for a particle size of about 30 nm can be reduced by more than 90% when the characteristics of the particulates are adapted to the oxidation potential of the catalyst employed, This corresponds to a total PM emission reduction of about 70% and demonstrates the high oxidation potential for other partial load operating points of a light-duty truck EURO 3 engine. It was found that the impact of modified engine adjustments on the particle contribution of smaller particles meets the technical requirements for an optimized reduction using an SCR catalyst based on V2O5/WO3/TiO2. Although the number concentration of particles with a size of <50 nm increases excessively, this results in a much higher efficiency of reduction of the particle number concentration by the catalyst, observed over the complete measurement range of the SMPS system used. The same result was also observed when EGR was used. The unavoidable NOx emission can be reduced, as usual, by running the catalyst in urea SCR, if necessary. In this context, the generation of particulates and their components was studied in the presence of urea SCR for selected stationary operating points depending on the urea dosage and fuel sulfur content to investigate the mechanisms of PM generation with the intention of optimizing emission control.