I used the peak blue tec, never had an issue, I was feeling cheap and bought the Walmart brand and 15 miles later, it's saying i have the wrong stuff. I went ahead and found the tank, it's under the back, all the way in the back center, right in-front of the hitch.. It has a snap on hose, was easy to get off. I just emptied it. I'm going to go by the blue def this morning, and put in 2.5 gallons. Then if need be, I'll reset my computer.