An Experimental Investigation on Rheological and Heat Transfer Performance of Hybrid Nanolubricant and Its Effect on the Vibration and Noise Characteristics of an Automotive Spark-Ignition Engine

This research aimed to investigate the feasibility of a new combination of hybrid nanolubricant that can enhance the vibration and noise characteristics of an automotive spark-ignition engine through a comprehensive study of rheological and heat transfer behavior. The ZnO-based mono (ZnO/5W30) and hybrid (ZnO–TiO 2 /5W30, 50:50) nanolubricants of 0.1 wt% and 0.5 wt% have been prepared, and their rheological behavior was examined by measuring the viscosity at different temperatures ranging from 298.15 K to 338.15 K (25 °C to 65 °C). The results showed that both engine oil and nanolubricant exhibit non-Newtonian behavior. The hybrid nanolubricant presented a comparatively high viscosity index than 5W30 engine oil and mono nanolubricant. The theoretical prediction of thermal conductivity using the Maxwell–Garnetts model showed an increasing trend with nanoparticles’ concentration in hybrid nanolubricant. Experiments were conducted on an unmodified MPFI engine operated under various speeds using regular engine oil and hybrid nanolubricant for investigating noise and vibration characteristics. A significant reduction in longitudinal and lateral vibration accelerations and a maximum decrease of 4.5 % in noise level are observed with hybrid nanolubricant. Graphic Abstract