## 4 Conclusions  
The study demonstrates that incorporating SiO\({}_{2}\) nanoparticles, modified with the silane coupling agent KH570, significantly enhances the physicochemical properties of both conventional and biolubricants. The surface modification facilitates better dispersion of SiO\({}_{2}\) nanoparticles, leading to a stable suspension in the form of clusters. The enhanced lubricants show slight increases in density and viscosity, along with a higher viscosity index, indicating improved thermal stability and flow resistance. These improvements can potentially lead to better lubrication performance, reduced friction, and wear, making the modified lubricants more suitable for demanding industrial and automotive applications. Chemical analysis, including TAN and TBN measurements, confirms that the addition of SiO\({}_{2}\) nanoparticles at various concentrations (0.25%, 0.50%, 0.75%, and 1.00%) does not introduce critical acidity levels and maintains a strong alkaline reserve. Furthermore, the ICP-OES analysis shows that the incorporation of SiO\({}_{2}\) nanoparticles mainly affects the silicon concentration, with minimal impact on other essential additives. This supports the feasibility of using SiO\({}_{2}\) nanoparticles without compromising additive stability. FTIR analysis confirmed the presence of SiO\({}_{2}\) and KH570 without altering the basic functional structures of the lubricants and biolubricants, indicating excellent chemical stability. The long-term stability of the nanolubricants was evaluated over a period of 77 days. Initial observations indicated well-dispersed samples, with visible sedimentation beginning around the 30 th day and becoming more pronounced by the 54 th and 77 th days. The bio-lubricants exhibited slightly higher sedimentation compared to conventional lubricants. Sonication time influenced stability, with longer sonication times (2.5 h) yielding better stability across different concentrations. UV-Vis spectrophotometry further emphasized the importance of optimizing sonication time to enhance the stability of the nanolubricants, with longer sonication times being beneficial, especially at higher nanoparticle concentrations. Future research could concentrate on additional domains to enhance and investigate the application of SiO\({}_{2}\) nanoparticles in lubricants. In particular, long-term performance testing in a range of industrial and automotive applications would be beneficial in determining the practical application of lubricants enriched with SiO\({}_{2}\) nanoparticles in real-world  
Figure 10: UV-Vis evaluation of SiO\({}_{2}\)/PLANTO MOT SAE 10W40 nanobiolubricants for 77 days at different concentrations with different sonication times. scenarios. To ensure their sustainable use, it would also be crucial to assess the safety and environmental impact of SiO2 nanoparticle-enhanced lubricants, including how they should be disposed of and any potential effects on ecosystems. In summary, the addition of surface-modified SiO2 nanoparticles to conventional and biolubricants enhances their physicochemical properties and stability without compromising chemical stability or additive integrity. The study highlights the importance of optimizing preparation conditions, particularly sonication time, to maximize the benefits of nanolubricants in various applications. Conceptualization, H.P., M.R. and M.B. ; methodology, H.P. ; formal analysis, H.P., M.R. and M.B. ; investigation, H.P. ; data curation, H.P. ; writing--original draft preparation, H.P. ; writing--review and editing, H.P., M.R. and M.B. ; visualization, H.P. ; supervision, M.R. and M.B. All authors have read and agreed to the published version of the manuscript. This research received no external funding. The raw data supporting the conclusions of this article will be made available by the authors on request. The authors wish to thank: Dott.