I'll be sending a sample of my used oil for analysis and could do a virgin on the ZF. There will be contaminants and likely a viscosity reduction in the used oil so not quite apples to apples. I am not sure that friction modifier content would show in an UOA/VOA unless it is an "element".I wouldn't put it beyond FCA to cut costs by reducing the cost of friction material by changing materials and adding more of some friction modifier to the fluid. Of course, all speculation. Maybe we could convince one of the oil guys to analyze both.