I bought a 2013 Ram Laramie longhorn 6.7 diesel dually used with 50332 miles. I love this truck. Since buying it ( about 2.5 months) I have put just over 3000 miles on it. I don't pull anything right now. The DEF gauge has not moved off full since the day I brought it home. This cant be normal can it? Anyone have thoughts on this or am I just looking for trouble?