in this work tribological characteristic of engine oil 20w50 mixed with 0.1% by weight of spherical nano particles of copper oxide of 20 nm and also spherical nano particles of titanium oxide of 21 nm has been investigated. Wear and friction are the two important factors of tribological characteristics. In this work after preparation of the nano fluids, two factors of wear and friction factor, using pin and plate tribometer, under constant load and at room temperature, once with pure engine oil and also with each nano fluids were measured and the results were compared to each other. The results indicated that presence of spherical nano particles of 20 nm copper oxide and 21 nm titanium oxide in lubricating oil, reduced the wear by 76.72% and 50% respectively and friction factor by 17.84% and 9.48% respectively, in comparison with engine oil without any nano particles. Therefore it can be predicted that spherical nano particles of copper oxide and titanium oxide, as an additive to engine oil, can play an effective role in increasing engine power and reduce engine exhaust emissions and fuel consumption.