This is an old topic, but now that 6.7 has been out for a couple of years I was hoping that someone has come across a def usage problem. I have a 2012 f-350 drw and the customer states that he went thru 40-50 litters of def with in 10 000 kms. I have no codes at all, performed dosing test and found it made 50 ml's of def. The hotline did not give me anything to chew on, so I was wondering what else I could look at and test. Thanks