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Engine lubricants play a vital role in ensuring smooth and reliable operation of internal combustion engine, primarily preventing corrosion, and reducing the risk of damage, keeping the engine cool by dissipating excessive heat, and enhancing combustion efficiency and reducing oil consumption. Now a days different nano size material additives are used for improving the lubricant's thermophysical properties. The purpose of this research is to improve tribological properties of the engine oil by adding different nanoparticle (cerium oxide, cerium doped, copper, copper doped, and chromium doped) to a base oil SAE 20W50 and evaluate and compare the enhancement in the properties. Three different concentrations: 0.1 w/w % 0.3 w/w % and 0.5 w/w % of each non-dopped and 0.1 w/w % for doped nanoparticle is taken and dispersed in base oil. Four different properties viscosity index, flash point, fire point and pour point are measured before and after engine operation. Upon the obtained result there is almost a linear relation between properties and concentration, most properties are improved by increasing the concentration of nanoparticle. Among all the properties the change in pour point have the highest which are 150 % with respect to base oil also the maximum viscosity index improve by 35 % and the maximum flash point and fire point are improve by 48 % and 25 % respectively. Among the entire nanoparticle almost all the doped particles show the maximum percent change at low concentration.

Keywords: Engine Oil, Nanoparticle, Cerium Oxide, Tribological Properties, Viscosity Index, Fire Point.