That’s funny. It certainly does seem odd.
Truck not using DEF?
Thread Starter
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Tuned
Joined: Sep 2016
Posts: 347
Likes: 12
Truck not using DEF?
Has anyone else noticed their truck sipping DEF and hardly using any at all? My first 5,000 miles I towed a 5,000 lb trailer about 1200 miles and went through an entire DEF tank. (In the total mileage) Now, I haven’t done any towing at all, I sit at 11,000 miles, and my DEF tank is still completely full from the fill up that occurred at 5,000 miles. What gives? Not that I’m necessarily complaining, but I want to make sure there’s nothing wrong. I know it doesn’t use much DEF when not towing, but it doesn’t appear to be using any! Thanks in advance for your input!
Fleet Mechanic
Joined: Aug 2017
Posts: 1,274
Likes: 26
From: St Louis Suburbs
My guess is something is wrong with the sending unit for the DEF gauge or the sensor is bad. Something is definitely wrong.
You shouldn't go from full to empty in 1,200 miles even if you are towing. It just doesn't burn through it that fast especially over that short distance.
Then after what sounds like 6,000 miles from a full DEF tank you should have burned through at least 1/2 of your DEF fluid.
I would have it checked out. If something is wrong I guess there is a possibility you wouldn't get a low DEF warning and then eventually the engine may not start.
You shouldn't go from full to empty in 1,200 miles even if you are towing. It just doesn't burn through it that fast especially over that short distance.
Then after what sounds like 6,000 miles from a full DEF tank you should have burned through at least 1/2 of your DEF fluid.
I would have it checked out. If something is wrong I guess there is a possibility you wouldn't get a low DEF warning and then eventually the engine may not start.
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Elder User
Joined: Apr 2017
Posts: 523
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From: Eagan, MN
Mine seems similar. The last time I put DEF in was towing my fifth wheel to FL. I am now back in MN, about 3K miles later. No towing in that 3K miles. The DEF needle has barely moved.
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Fleet Mechanic
Joined: Aug 2017
Posts: 1,274
Likes: 26
From: St Louis Suburbs
It should go through an entire tank of DEF fluid is approximately 11,000 miles if you are not towing. The volume and size of the DEF tank is specifically designed to get you through a 10,000 mile oil changer interval with some reserve. I could see how after 3,000 miles it may barely move because it could have been topped off pretty full to begin those 3,000 miles. Once it starts to move it will be pretty predictable how much it goes down compared to how many miles you drive.
Hotshot
Joined: Apr 2013
Posts: 10,118
Likes: 650
From: NH
The part about the gauge not moving in 6k miles would make something seem not right. I've got 1500 miles on my new truck, and have only towed a snowmobile trailer about 20 miles...DEF gauge is creeping down towards the 3/4 mark.
Fleet Mechanic
Joined: Aug 2017
Posts: 1,274
Likes: 26
From: St Louis Suburbs
He is saying the truck used all the DEF in the first 5,000 miles...of which, he was towing for 1200 miles. I think that is perfectly plausible. My 2017 dually used up basically 7 gallons in 5k miles during my towing season.
The part about the gauge not moving in 6k miles would make something seem not right. I've got 1500 miles on my new truck, and have only towed a snowmobile trailer about 20 miles...DEF gauge is creeping down towards the 3/4 mark.
The part about the gauge not moving in 6k miles would make something seem not right. I've got 1500 miles on my new truck, and have only towed a snowmobile trailer about 20 miles...DEF gauge is creeping down towards the 3/4 mark.
Thread Starter
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Tuned
Joined: Sep 2016
Posts: 347
Likes: 12
He is saying the truck used all the DEF in the first 5,000 miles...of which, he was towing for 1200 miles. I think that is perfectly plausible. My 2017 dually used up basically 7 gallons in 5k miles during my towing season.
The part about the gauge not moving in 6k miles would make something seem not right. I've got 1500 miles on my new truck, and have only towed a snowmobile trailer about 20 miles...DEF gauge is creeping down towards the 3/4 mark.
The part about the gauge not moving in 6k miles would make something seem not right. I've got 1500 miles on my new truck, and have only towed a snowmobile trailer about 20 miles...DEF gauge is creeping down towards the 3/4 mark.
As for another 6,000 miles without the needle even moving, I’m confused. 😕 I did have the gas tank TSB done, but that’s it. Not sure if it requires moving the DEF tank or not.
Thread Starter
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Tuned
Joined: Sep 2016
Posts: 347
Likes: 12
Ok, well for all you diesel experts out there, this is my first one, so I don't know much about it and appreciate the help.
Assuming the truck magically isn't using any DEF, what are the repercussions of that? Does it have anything to do with my DPF at all, or does it spray the DEF only in the exhaust to remove some of the toxic fumes, and not prior to the DPF? I can still smell the truck doing regens, so I know that is still happening correctly, but my DEF gauge is still sitting at 100%,so I'm not sure if anything is being sprayed. I plan on waiting to see if I get any "500 miles remaining" messages before I take it in. I'm curios to know the computer logic as well...does it only give the warning based on the gauge readings? Am I going to wake up one day and the truck suddenly be full-on limp mode when it actually does run out, but still displays full on the gauge? Is the a test upstream at the nozzle to determine if DEF is actually coming out? So many questions...Thoughts?
Assuming the truck magically isn't using any DEF, what are the repercussions of that? Does it have anything to do with my DPF at all, or does it spray the DEF only in the exhaust to remove some of the toxic fumes, and not prior to the DPF? I can still smell the truck doing regens, so I know that is still happening correctly, but my DEF gauge is still sitting at 100%,so I'm not sure if anything is being sprayed. I plan on waiting to see if I get any "500 miles remaining" messages before I take it in. I'm curios to know the computer logic as well...does it only give the warning based on the gauge readings? Am I going to wake up one day and the truck suddenly be full-on limp mode when it actually does run out, but still displays full on the gauge? Is the a test upstream at the nozzle to determine if DEF is actually coming out? So many questions...Thoughts?