## 3 Results and Discussion
Furthermore, it can be understood that as the temperature rises, the oil or additive molecules increase their motion, resulting in a decrease in the viscosity of the fluid. The viscosity values of the oils in both cases, with and without the additive and at different experimental temperatures, are listed in Table 6. To observe and evaluate more visually, these results are presented in Figure 5, depicting the relationship between the viscosity of the tested oils A, B, and C at various temperatures. From these results, we can have a visual understanding of the influence of temperature ranges on the viscosity of the oils. Accordingly, within the temperature range from 25 \({}^{\circ}\)C to 65 \({}^{\circ}\)C, the viscosity of the oil decreases with a lower magnitude compared to the range from 65 \({}^{\circ}\)C to 85 \({}^{\circ}\)C. This is reflected in the slopes of the graphs in Figure 5. In the case of the additive at a concentration of 0.5%, the trend of viscosity reduction with temperature occurs similarly to the case without the additive. However, for oil A, the magnitude of viscosity reduction within this temperature range is smaller, as indicated by a smaller slope. This could be attributed to the fact that oil A initially has the lowest viscosity among the three oils, and the additive enhances the effectiveness of viscosity reduction more in oils with higher initial viscosities. An appropriate amount of additive helps enhance the lubricating properties of the base oil. In this case, the additive has reduced the impact of temperature on the viscosity of the oil. The additive consists of high-hardness metal oxide particles that act as better thermal conductors than base oil. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \multirow{2}{*}{**Oils**} & \multicolumn{6}{c}{**0\% Fly-Ash Additive**} & \multicolumn{6}{c}{**0.5\% Fly-Ash Additive**} \\ \cline{2-10}  & **25 \({}^{\circ}\)C** & **40 \({}^{\circ}\)C** & **65 \({}^{\circ}\)C** & **75 \({}^{\circ}\)C** & **85 \({}^{\circ}\)C** & **25 \({}^{\circ}\)C** & **40 \({}^{\circ}\)C** & **65 \({}^{\circ}\)C** & **75 \({}^{\circ}\)C** & **85 \({}^{\circ}\)C** \\ \hline \multirow{2}{*}{A} & 80.315 \(\pm\) & 68.494 \(\pm\) & 45.475 \(\pm\) & 38.365 \(\pm\) & 31.866 \(\pm\) & 91.411 \(\pm\) & 81.031 \(\pm\) & 62.521 \(\pm\) & 47.119 \(\pm\) & 42.329 \(\pm\) \\  & 4.266 & 3.459 & 2.791 & 2.557 & 2.351 & 4.654 & 2.660 & 3.931 & 3.094 & 2.155 \\ \multirow{2}{*}{B} & 139.799 & 128.901 & 96.375 \(\pm\) & 69.769 \(\pm\) & 54.831 \(\pm\) & 148.443 & 139.745 & 107.351 & 76.851 \(\pm\) & 60.908 \(\pm\) \\  & \(\pm\) 9.893 & \(\pm\) 8.061 & 6.171 & 5.569 & 4.200 & \(\pm\) 9.498 & \(\pm\) 9.339 & \(\pm\) 6.984 & 5.763 & 4.138 \\ \multirow{2}{*}{C} & 183.545 & 168.506 & 130.911 & 98.970 \(\pm\) & 66.076 \(\pm\) & 198.468 & 184.055 & 144.45901 & 110.323 & 77.061 \(\pm\) \\  & \(\pm\) 12.854 & \(\pm\) 9.886 & \(\pm\) 8.332 & 6.026 & 3.922 & \(\pm\) 10.470 & \(\pm\) 10.858 & \(\pm\) 8.029 & \(\pm\) 7.823 & 4.386 \\ \hline \end{tabular}
\end{table} 
Table 6: Viscosity vs. temperature (mPa.s). Figure 4: Shear pressure with different temperature of oil C. (**a**) 0% fly-ash additive. (**b**) 0.5% fly-ash additive. Figure 5a illustrates that the viscosity of oil A decreases from 80.315 mPa.s to 31.866 mPa.s as the temperature changes from 25 \({}^{\circ}\)C to 85 \({}^{\circ}\)C, whereas without the additive, the viscosity changes from 91.411 mPa.s to 42.329 mPa.s when the temperature increases from 25 \({}^{\circ}\)C to 85 \({}^{\circ}\)C. Thus, at 25 \({}^{\circ}\)C, the viscosity increased by 13.8% with the addition of the 0.5% additive. In contrast, at 85 \({}^{\circ}\)C, this value increased by 32.8% compared to the case without the additive. It can be observed that the additive played an important role in increasing the viscosity of the oil by enhancing the load-carrying capacity of the lubricating oil.