This experimentation explores the usage of three types of biodiesel consisting of palm, jatropha and cottonseed incorporated in a single-cylinder four-stroke CI engine to evaluate the performance, emission and combustion indices. The objective of this study is to prepare biodiesel blends of three types: (i) primary, (ii) binary and (iii) ternary, and investigate their behaviors to identify the optimal blends that produce the lowest emissions and adequate performance with no significant engine modifications. Experimental investigations carried out in this study indicate that by increasing biodiesel quantity in the blend, a rise in brake thermal efficiency and a marginal increase in brake specific fuel consumption were deduced. P30 blend was superior among the biodiesel blends, showing a maximum thermal efficiency of 36.83%. Biodiesel blends were reported to emit lower NOx emissions at higher loads and increased NOx at low loads compared to diesel. Culminated values of NOx were shown by CS30 (601 ppm); similarly, binary blend PJ30 showed a curtailed amount of NOx (497 ppm) at 20 N-m loading. Lower emissions of unburnt hydrocarbon and carbon monoxide are noticed for biodiesel blends with values lying in a range of 35–40 ppm and 0.04%, respectively, while the smoke emissions escalated for biodiesel blends reaching up to 76% for PJCS20. Among combustion indices, biodiesels showed lower heat release rate (HRR) and lower maximum pressure than diesel and increasing blend ratio resulted in lower HRR and higher pressure. P10 blend was observed to be providing better performance and emissions (lowered HC and CO) compared to all other blends. © 2021, Akadémiai Kiadó, Budapest, Hungary.