Molybdenum containing friction modifiers are generally expected to perform well in reducing boundary friction and organic friction modifiers are thought to be more effective under mixed conditions.
As can be seen from Table 2, adding 2 wt% fatty diamine salt or monoamine salt alone to Baseline Oil A reduces the friction in the boundary regime slightly, but appears to increase mixed friction. Adding 0.2 wt% (90ppmw)of the organo-molydenum compound alone to Baseline Oil A reduces both the boundary and mixed friction slightly.
Adding a much larger amount of the organo-molybdenum compound (0.9 wt%, 400ppmw) alone leads to reduced boundary and mixed friction, but using an undesirably large amount of molybdenum.
When 0.9 wt% (400 ppmw) of the organo-molybdenum compound is added to Baseline oil A with 0.5 wt% of a monoamine salt (Ethomeen) , friction actually increased both in the boundary and mixed regime, near to the level of Baseline oil A.
However, when the organo-molybdenum compound at a lower level (90ppm, 0.2wt%) is combined with 0.5 wt% of a diamine salt, significant synergistic improvements in both boundary friction and mixed friction are seen.