Paper presents an exhaust gas emission investigation for a high speed turbocharged direct injection diesel engine MAN D0826 LOH15 during the fuel and air mass flow variation. Emission analysis is based on a two measurement sets at two different engine rotational speeds (1500 rpm and 2400 rpm). The analyzed diesel engine operates with a standard diesel fuel. Measured emissions were nitrogen oxides (NOx), unburned hydrocarbons (HC) and soot emissions. Calculated emissions were carbon dioxide (CO2) emissions by using equations from the literature. For the observed diesel engine, much higher NOx and HC emissions were obtained at the lower engine rotational speed. Soot emission of the analyzed engine, in general, does not have to depend on engine rotational speed. Calculated CO2 emissions depend primarily on the fuel mass flow and the carbon mass fraction in used fuel.