[davemitchell59]

[QUOTE For my new truck (2019) dealer tech told me I could fill it up with 5 gallons when the message appears. He said you can fill it up to the point where it runs out of the fill port. I have only tried a 5 gallon fill one time so far and it did not run over the fill port.[/QUOTE]


That's what I was told or read for my 2016 3500 GMC. And I've read where it is bad for it to add before the warning. I've only filled twice. Both times the warning came on at inconvenient times, so put on a couple hundred miles before adding DEF. 5 gallons and no problems. Just wondering if this thread is changing my mind about that approach. I may have to have a conversation with the maintenance department at the next oil change.