The aim of this study is to investigate the effects of the pilot fuel injection (10% by mass) application and the increased boost pressure (10% in mbar) in a diesel engine fueled with the ethanol-butan-2-ol-fossil diesel fuel mixtures on combustion characteristics. The experimental results were analyzed statistically and based on energy balance. Engine tests were conducted using the conditioned intake air and the fuel spraying 45 mg/stroke into the cylinder per cycle. In the result of this study, it was observed that the ignition delay and combustion noise decreased significantly with the increase in the alcohol content in fuel mixture during pilot fuel injection application. The lowest ignition delay and the combustion noise was obtained with the use of E20B4. However, the biggest deviation in the ignition delay and the combustion noise values was monitored with the use of E20B4 when the pilot fuel was applied. It has been calculated that higher heat release rates occur under all conditions compared to neat PBDF when using the alcohol-PBDF fuel blends. The improvements were obtained in the expansion stroke of log P-V curves during the use of E20B4 when the boost air pressure was increased by 10%. It has been determined that there is a sudden increase trend in CO2 and NO emissions with pilot fuel injection application. However, it was observed that the increase in boost air pressure is not have a significant effect on the formation of CO2 and NO emission. In the tests, it was analyzed that the deviation in NO emission values was quite low. The results show that pilot fuel injection should be preferred when using alcohol-diesel mixture up to 25% by volume in diesel engines.