## 3 Results and Discussion  
### Characterization and Assessment of Nanolubricants and Nanobiolubricants  
The kinematic viscosity at 40 \({}^{\circ}\)C and 100 \({}^{\circ}\)C, the density at 15 \({}^{\circ}\)C, and the viscosity index of all samples, including pure lubricants/biolubricants and nanolubricants/nanobiolubricants, are comprehensively measured and presented in Tables 5 and 6 for comparison and analysis. These measurements provide critical insights into the performance characteristics of each lubricant type under various conditions. Both nanolubricants and nanobiolubricants exhibit a consistent dark yellow appearance and a characteristic smell across all samples, indicating no significant changes in these sensory properties with the addition of SiO\({}_{2}\) nanoparticles. For nanolubricants, the density increases slightly with higher concentrations of SiO\({}_{2}\), from 0.8769 g\(\cdot\)cm\({}^{-3}\) for pure lubricant to 0.8842 g\(\cdot\)cm\({}^{-3}\) for 1.00% SiO\({}_{2}\) nanolubricant. Similarly, nanobiolubricants show a gradual increase in density from 0.8719 g\(\cdot\)cm\({}^{-3}\) for pure biolubricant to 0.8770 g\(\cdot\)cm\({}^{-3}\) for 1.00% SiO\({}_{2}\) nanobiolubricants. The increase in density suggests that the incorporation of SiO\({}_{2}\) nanoparticles results in a denser formulation due to the addition of solid particles. The viscosity at 40 \({}^{\circ}\)C and 100 \({}^{\circ}\)C show a slight increase with higher SiO\({}_{2}\) content for both nanolubricants and nanobiolubricants. For nanolubricants, the viscosity at 40 \({}^{\circ}\)C ranges from 97.3 cSt (pure) to 99.9 cSt (1.00% SiO\({}_{2}\)), and at 100 \({}^{\circ}\)C from 13.5 cSt (pure) to 14.0 cSt (1.00% SiO\({}_{2}\)). For nanobiolubricants, the viscosity at 40 \({}^{\circ}\)C ranges from 87.0 cSt (pure) to 90.3 cSt (1.00% SiO\({}_{2}\)), and at 100 \({}^{\circ}\)C from 13.7 cSt (pure) to 14.4 cSt (1.00% SiO\({}_{2}\)). The slight increase in viscosity indicates improved resistance to flow, which can enhance lubrication properties and reduce wear [40; 49; 50]. The viscosity index shows improvement with increasing SiO\({}_{2}\) content for both types of lubricants. Nanolubricants' viscosity index rises from 138 (pure) to 143 (1.00% SiO\({}_{2}\)). Nanobiolubricants' viscosity index increases more significantly, from 160 (pure) to 166 (1.00% SiO\({}_{2}\)). A higher viscosity index indicates better stability of the lubricant's viscosity across temperature changes, which is beneficial for maintaining performance under varying operating conditions [51]. The TAN values for all samples, including the base lubricants (Mistral 15W40 and PLANTO MOT SAE 10W40) and nanolubricants, are below 3.0 mg(KOH)\(\cdot\)g\({}^{-1}\). This is generally considered acceptable for lubricants. The slight variations among the samples are not significant enough to cause concern, indicating that the addition of SiO\({}_{2}\) nanoparticles does not significantly increase acidity and might even help in stabilizing it. However, as the concentration of SiO\({}_{2}\) increases, there is a gradual increase in acidity. While these values are not immediately critical, the trend suggests that higher concentrations of SiO\({}_{2}\) could lead to higher acidity over time. The TBN values remain stable and high, around 10.3 to 10.7 mg(KOH)\(\cdot\)g\({}^{-1}\), across all samples of nanolubricants and around 9.5 to 9.9 mg(KOH)\(\cdot\)g\({}^{-1}\) for nanobiolubricants. This indicates that the nanolubricants have a strong capacity for neutralizing acids, and the addition of SiO\({}_{2}\) nanoparticles does not adversely affect the alkaline reserve of the lubricants. Figure 3: Agilent Cary 100 UV-Visible Spectrophotometer. This stability suggests that the nanolubricants, despite having a slightly higher acidity, could potentially offer enhanced corrosion resistance, as suggested by recent research on the use of metal and oxide nanoparticles [52; 53]. However, specific corrosion tests would be required to confirm their effectiveness in protecting against corrosion.