Hi all I am on tank of gas # 6 on my new to me truck and thrnDEF fluid gage has barely even moved How long do you get on a tank of DEF fluid and how big is the reservoir? Thanks
In theory, you should need DEF about the same time you need an oil change. But there are a LOT of variables to that.
Your DEF gauge is probably working just fine. You shouldn't need to fill after 6 tanks of fuel. According to Cummins, DEF consumption is 3% - 5% of your total fuel consumption.