http://forums.tdiclub.com/showthread.php?s=e50ba245b8cd46e8641d55028a5f0324&t=18757 This is old, but interesting.
Theoretically, you could have one UOA with Fe @ 50ppm, another with 25ppm, but the oil that came back with higher Fe is actually protecting the engine better.
But since the regular analysis will not indicate the severity of the actual wear this is where ferrography comes into play. Look at both of the spectroanlysis oil samples taken. Based on those you would not suspect that the 0w30 engine would have any problems because the wear metals are so low. The fact is the type fo wear that is occuring is severe. The oil is working but it is not preventing dangerous types of wear from occuring.