The fluctuations in the combustion process of diesel fuel with hydrogen addition in an internal compression ignition engine were investigated. The cyclic combustion pressure was measured and its cyclic oscillations were expressed by indicated mean effective pressure per cycle. The statistical and multifractal analyses applied to the corresponding time series showed considerable changes in the engine dynamics for hydrogen percentages ranging from 5% to 20%. The study for the diesel engine was carried out for 11 various operating points and at the speeds ranging from 1200 to 2000 rpm. Also, exhaust gas components were analyzed. The hydrogen addition was found to affect the differentiation of the indicated mean effective pressure in the engine. A reduction of CO₂ emissions and an increase in NOx emissions were registered.