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Cooling of internal combustion engines are necessary to prevent reaching high temperatures that would damage the engine block. For this reason, studies on more efficient cooling of internal combustion engines are frequently encountered in the literature. This becomes even more important if the internal combustion engine is supercharged. These engines are mostly cooled by liquid fluids, while some are cooled by air. Considering this point, in this theoretical study, effect of using of water, water + Al2O3, water + CuO, ethylene glycol, water + ethylene glycol, water + ethylene glycol + Al2O3 or water + ethylene glycol + CuO in the cooling system of a diesel engine on the amount of heat removed is investigated, respectively. In daily life, considering that the freezing temperature of water is relatively higher than the freezing temperature of ethylene glycol, water + ethylene glycol mixture is used instead of single water in engine cooling systems. Considering this situation, in this study, usage of water-ethylene glycol mixture and usage of single water or usage of various nano-fluids are thermally compared. For this aim, primarily, the effect of nano-particle volumetric ratio in the mixtures on the thermophysical properties such as density, specific heat, and thermal conductivity of the related nano-fluid is investigated. Then, using these new thermophysical properties, the effect of fluid or nano-fluid on the amount of heat to be removed from the engine block is investigated. According to this; among the examined fluids, the fluid with the highest density is 47.5% water + 47.5% ethylene glycol + 5% CuO, while water has the highest specific heat. The highest value among the thermal conductivity values that are calculated using various relations belongs to 49.75% water + 49.75% ethylene glycol + 0.5% CuO fluid according to the Wasp Model. The fluid with the highest mass flow rate is 47.5% water + 47.5% ethylene glycol + 5% CuO fluid which has the highest density. According to these data, the usage of nano-fluids provided an increase nearly as 15% in the amount of heat removed from the engine block thanks to increasing in density and specific heat. [ABSTRACT FROM AUTHOR]