[en] Highlights: • The suspension of ZnO nanoparticle and 10W40 is provided as nano-lubricant. • Viscosity of concentration up to 2 vol% is measured at temperatures of 5–55 °C. • The nano-lubricant exhibits non-Newtonian shear thinning behavior. • A correlation is introduced for viscosity in terms of temperature and concentration. • A multi-layer artificial neural network is used to predict the desired parameters. In the present study, rheological behavior of ZnO/10W40 nano-lubricant is investigated by an experimental approach. Firstly, ZnO nanoparticles of 10–30 nm were dispersed in 10W40 engine oil with solid volume fractions of 0.25–2%, then the viscosity of the composed nano-lubricant was measured in temperature ranges of 5–55 °C and in various shear rates. From analyzing the results, it was revealed that both of the base oil and nano-lubricants are non-Newtonian fluids which exhibit shear thinning behavior. Sensitivity of viscosity to the solid volume fraction enhancement was calculated by a new correlation which was proposed in terms of solid volume fraction and temperature. In order to attain an accurate model by which experimental data are predicted, an artificial neural network (ANN) with a hidden layer and 5 neurons was designed. This model was considerably accurate in predicting experimental data of dynamic viscosity as R-squared and average absolute relative deviation (AARD %) were respectively 0.9999 and 0.0502.