and fuel specific gravity, viscosity and heating value. As a result, more COCO blends are needed to produce the same amount of energy due to its higher specific gravity and lower heating value in comparison to conventional diesel. Fig. 3 shows the net heat release rate for all the fuel systems in kilojoules (kJ) per degree of crank angle at 3000 rpm. It has been observed that 10 to 30% COCO blends produce similar heat release rate as conventional diesel, although the average calorific value of COCO blends is about 6% lower than conventional diesel. This is expected as a slight increase in the density of COCO blends could result in ignition delay which allows more fuel to mix within combustible limits during the delay [7]. Hence the similar heat release rate is obtained. However, the tendency of 40/COCO and 50/COCO fuels show lower maximum heat release rate compared to others. This could be attributed to lower internal energy and slow burning. The effects of COCO blends on cylinder pressure are shown in Fig. 4. It has been