Manual 1.9tdi 6spd OX1 gearbox here with quattro rear diff and over 200,000 miles on the original drivetrain oils. No indication anywhere as to wether the lifetime life of the oils really is that, for as long as the car is alive. Plenty of threads where people say they've changed the oil because they thought it a good idea and some of them saying better gearchanges. I can well believe that some of this might be in peoples heads. My gearchanges are fine, Im not aware of any diff problems and wonder should I just leave it alone. No oil leaks so no need to top up. Can it be true that the oil in there will last forever? Has anyone ever put this to some sort of real objective test like measure power at wheels before and after a torsen diffs oil change?