Being someone who is seriously looking into buying a diesel and doesn't own one yet, I'm wondering if someone can answer why a flush is needed if the passive tank is empty and the active tank is giving warnings. Why would you need to flush an empty tank? Since the active tank will be used first, what's the point of flushing this if you drive it daily? I can certainly understand if during oil change time, the active tank is not empty but only the active tank would need to be flushed, no?

This DEF fluid seems to be one more thing to worry about; especially from a potential purchaser from a moderately cold climate (Canada) who doesn't require this system due to government regulations.

Santo