In the automotive field, the main manufacturers have long been committed to building vehicles with a lower environmental impact to safeguard air pollution and human life. Nowadays the most efficient way to control the emissions on light-duty vehicles is through two different test procedures that have been exploited during this project: roller bench test procedure and RDE (real driving emission) test procedure. The main goal of this study is to develop a numerical investigation to assess the improvement in terms of NOx and CO2 emissions reduction, on a diesel F1A Daily which has been installed on light-duty vehicles, making than a comparison between the model year nineteen (MY19) and the model year twenty-one (MY21).