Ram 2500 DEF fluid

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.

The DEF tank on a 2016 2500 is 5.5 gallons.

The DEF gauge isn't linear. It will show full until its about half a tank, then it will quickly drop down towards empty. One day you will get a warning that DEF is low, that is usually when I fill up. If you don't fill up then, you'll eventually start getting messages saying 250 miles to shutdown, etc.

During the summer we take shorter trips, so I just dump 2.5 gallon jugs in when I get the low DEF warning. In the winter we take a long trip, so I usually fill the DEF at a pump, so I can fill the tank.

samhain7 wrote:
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

Your problem is you have been putting "GAS" in your Diesel Truck.

Your gas truck will run forever without filling the DEF tank. :W

The answer to your question is in the owners manual.

It varies. You will use more when towing than when not towing. It also makes a difference in how big the DEF tank is. My understanding is to expect around 1000 miles for each gallon of DEF when not towing.