Friction modifiers (FM) work different in different lubrication regimes. If you are operating in hydrodynamic areas, only the viscosity will affect the friction and the lighter the viscosity the lower the friction. Be sure the viscosity is at the conditions of engagement as temperature, pressure and shear rate will all effect viscosity. Ball bearings have very high pressures and the oil in those areas is operating at what is called elastohydrodynamic regime. Under high pressure PAO is less viscosity than same viscosity mineral oils not under pressure, so PAO is lower friction and could be a FM.
When in boundary areas, the surface active chemistries in the oil and not viscosity affect the friction. Items such as metal deactivators, sulfur EP, zinc phosphorus AW, fatty acid esters and moly carbamates are all friction modifiers. Sometimes you want the friction to be low and others for it to be higher. If power is being transferred through the device you need sufficient friction so the device, like a clutch, does not slip. If you want fuel economy; at the piston rings, a low coefficient of friction is what you want. To know which type is best for which application is difficult to say since operating conditions also change. There are three major categories of zinc types that operate at different temperatures, thus a diesel engine, a gasoline engine and a natural gas engine will all have different piston ring temperatures and different zinc requirements for just FM. Throw in camshaft friction and one type will not work best for both.
Therefore it is difficult to say which chemistry goes with what application.
When in boundary areas, the surface active chemistries in the oil and not viscosity affect the friction. Items such as metal deactivators, sulfur EP, zinc phosphorus AW, fatty acid esters and moly carbamates are all friction modifiers. Sometimes you want the friction to be low and others for it to be higher. If power is being transferred through the device you need sufficient friction so the device, like a clutch, does not slip. If you want fuel economy; at the piston rings, a low coefficient of friction is what you want. To know which type is best for which application is difficult to say since operating conditions also change. There are three major categories of zinc types that operate at different temperatures, thus a diesel engine, a gasoline engine and a natural gas engine will all have different piston ring temperatures and different zinc requirements for just FM. Throw in camshaft friction and one type will not work best for both.
Therefore it is difficult to say which chemistry goes with what application.
