Lubricants minimize friction, heat, friction, and wear of moving or rotating parts. They serve several essential roles in IC engines, including lubricating, cooling, cleaning, suspending, and corrosion protection of metal surfaces. Nanolubricants have gained popularity due to their exceptional rheological, tribological, and wear resistance properties. The ability to design and anticipate the behavior of a lubricated mechanical system requires an understanding of rheological and heat transfer performance. This article explored the stability, rheological, and heat transfer performance of a novel ZnO-TiO2/5W30 hybrid nanolubricant to employ it as an effective lubricant for spark-ignition engines. The stability of the hybrid nanolubricant is analyzed using a zeta potential test, UV-vis spectrophotometer, and visual inspection. The zeta potential value of 46.3 mV for 0.1 wt.% ZnO-TiO2/5W30 hybrid nanolubricant indicates that it is stable at this concentration. The sample passed the stability test after seven days of preparation. The authors observed that the zeta potential value falls faster as the nanoparticle concentration rises in the nanolubricant. According to UV-Visible spectroscopy results, the dispersion of the 0.1% hybrid nanolubricant is comparatively more stable than the 0.5% hybrid nanolubricant. At higher temperatures, non-Newtonian shear-thinning behavior is seen in both the hybrid nanolubricant and base engine oil (5W30). The hybrid nanolubricant has a viscosity index of 171, which is higher than that of the base lubricant and indicates a minimal change in kinematic viscosity with temperature. Compared to the base lubricant, the 0.1 wt.% hybrid nanolubricant demonstrated a 4% increase in thermal conductivity at higher temperatures. Hybrid nanolubricant’s improved characteristics make it ideal for use in SI engines.
