## 4 Discussion  
From the results we are able to get an understanding of how the IL and NG additives would affect a system in the event of a loss-of-lubrication event. The results of the ball-on-disk, loss-of-lubrication experiments show that both the IL and the NG increase the time to the initiation of scuffing. These additives have a synergistic effect, where together the increase in time to scuffing onset is greater than the sum of the increase from each component alone. The reciprocating loss-of-lubrication experiment also shows an increase in the time to scuffing initiation when including the additives over that of the base oil. In this experiment, the time to scuffing initiation increased with higher IL concentration, demonstrating that even at higher concentration of IL the two additives are able to perform together. In contrast, when evaluating load at which scuffing occurs, the results suggest a discord between the two additives. We observed an increase in the scuffing load compared to the unadditivized oil when using either the IL or NG alone, however when the additives were together, we observed a much lower scuffing load. This lower load is likely the reason why we were unable to complete the friction mapping experiments. We were able to complete the loss-of-lubrication experiments for the oil containing both IL and NG additives because the applied load was less than the scuffing load even though the speeds were similar to the scuffing load experiments. Starved lubrication through removal of the oil source and increasing the load both bring the surfaces of the steel into more intimate contact. Each additive alone tends to increase the resistance to scuffing for the two methods of increasing contact severity. However, the propensity to scuff behaves very differently between these two methods for the combination of IL and NG additives. The tribofilms that presumably prevent scuffing did not seems to interfere with one-another during starved lubrication  
Figure 7: Coefficient of friction during reciprocating pin-on-flat, loss-of-lubrication experiments. The dotted line shows the time of lubricant removal. but did not offer the same protection at increased loads during full-film lubrication. The reason for this difference may be the run-in processes that the two scuffing determination methods experience, resulting in different surface roughness and possibly different tribofilms. However, that run-in process is complex, as the following analysis of coefficient of friction reveals. The last observation was with the COF and run-in behavior of the steel when using the different oil blends. During the ball-on-disk, loss-of-lubrication experiment, little difference was observed between the baseline oil and the two blends with IL at the key points during running in and just before initiation of scuffing. This result is in agreement with the friction mapping results where differences in COF only begin to be significant at lower entrainment speeds. However, during the scuffing load experiments, a high COF was observed for both blends containing IL for all loads. We can see from the surface roughness of friction mapping wear tracks that the surfaces run-in less with the blends containing IL as the IL seems to hinder the smoothing effect of run-in. The hindrance of run-in resulting in a rougher surface can be seen to increase the COF in the mixed lubrication regime of the IL-containing blend over that of the baseline oil at entrainment velocities below 2 m/s in Figure 6. Another contrast in COF was observed for the plain NG blend when compared to baseline oil. The NG blend had a similar COF to the baseline oil in both scuffing load and friction mapping experiments, however during the ball-on-disk, loss-of-lubrication experiment the COF was significantly lower. The low \(p\)-number of 0.003 and 0.104 indicate a low probability of this difference being due to sampling error.