The EU is actually working not only on tightening emission reduction rules (standard Euro 6 up to Euro 6d), but also on improving testing procedures for pollutant emissions and fuel consumption of light-duty vehicles. Emissions resulting from compression ignition diesel engines contains high levels of nitrogen oxides (NO_x), particulate matter (PM2.5 and PM10), hydrocarbons (HC) and small quantities of carbon monoxide (CO) and carbon dioxide (CO₂). In order to reduce the emissions level from exhaust gases, catalytic solutions for intake system can be used. For this study it was tested a Diesel engine and a sodium borate water solution added to intake air,  in order to reduce the pollutant amount from exhaust gases. The researches presented in the present paper were made on a AVL CR Diesel Single Cylinder Research Engine 5402. In the research tests made on the experimental engine, a large set of data were collected for the analysis of combustion quality and efficiency. Sodium borate water solution added to the intake can be a real alternative to the pollution control strategies and also for long term engine cleaning methods.