The chemical property of fuel seriously affects it’s the spray and atomization. Better atomization contributes to higher efficiency and less exhaust emissions. Fuel characteristics can be improved by addition of additives in the fuel. In this study, n-hexane additive was added in diesel and two different biodiesel fuels. The additive decreased the cetane number, density and viscosity values of the test fuels while increased the lower calorific value. As a result of the experiments, it was seen that there was an increase in the engine torque, engine power and specific fuel consumption by adding additives. Engine torque increased by 1.09% in DHX16 fuel compared to D0 fuel, 5% in RHX16 fuel compared to R0 fuel and 3.29% in CHX16 fuel compared to C0 fuel. The ignition delay decreased with additives and the cylinder pressure increased. The reduction in CO emissions was 7.07% in DHX16 fuel, 12.86% in RHX16 and 12.85% in CHX16 fuel. This decrease in HC emissions was 17.04%, 18.42% and 16.66%, respectively. In terms of NOX emissions, there was an increase of 4.73% in DHX16 fuel mixture compared to D0 fuel, 0.98% in RHX16 fuel mixture compared to R0 fuel and 2.01% in CHX16 fuel mixture compared to C0 fuel due to the improvement of combustion.