In this project, rheological variations of hybrid nano-lubricant with temperature and solid volume fraction have been tested. Nano-lubricant was prepared by dispersing copper oxide (CuO) nanoparticles and multi walled carbon nanotubes (MWCNTs) to SAE40 engine oil. The viscosity of volume fractions 0.0625–1% was measured in temperatures 25–50 degree of celesius and different shear rates. The results showed that in concentration 1 vol.%, the viscosity of hybrid nano-lubricant was 29.47% more than the viscosity of the base oil. The study conducted on rheological behavior proved that nano-lubricant and pure oil were non-Newtonian so they followed Ostwald de Waele relationship. The estimation of indices revealed that the behavior is shear thinning. Due to disability of the current models to predict nano-lubricant viscosity,a new correlation in each temperature in terms of solid volume fraction was proposed. The accuracy of correlations in different temperatures varied from 99.64 to 98.06%. Sensitivity of nano-lubricant to 10% increase in concentration was estimated. Also, an Artificial Neural Network was designed by multilayer perceptron method including two hidden layers, one of which had five neurons and the other one had four neurons. R-squared, MSE, and AARD were calculated 0.9966, 0.00002081, and 0.0055, respectively
