DEF notification every 500 miles
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Joined: Aug 2018
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DEF notification every 500 miles
Good afternoon all,
I recently traded my f250 in for a F350 DRW for better towing. I had put 2.5 gallons of DEF in prior to my last trip to top it off. 500 miles of towing later (16,000 fth wheel) and I got the notice of 500 miles warning came on. I put in 2 gallons and made the trip home and the 500 mile warning light is on again. That doesn't seem right as I used to get approximately 1000 per gallon on my 250. Any suggestions
I recently traded my f250 in for a F350 DRW for better towing. I had put 2.5 gallons of DEF in prior to my last trip to top it off. 500 miles of towing later (16,000 fth wheel) and I got the notice of 500 miles warning came on. I put in 2 gallons and made the trip home and the 500 mile warning light is on again. That doesn't seem right as I used to get approximately 1000 per gallon on my 250. Any suggestions
Super Moderator
Joined: Aug 2008
Posts: 37,379
Likes: 1,863
From: Frederick, MD
don't put anymore in. It is confused. Let it get down to less than 200 to empty. Trip or no trip, I never fill it until it is less than 200 to empty.
May have to make a trip to the dealer to do a reset.
May have to make a trip to the dealer to do a reset.
Fleet Mechanic
Joined: Dec 2015
Posts: 1,521
Likes: 412
From: Washington Coast
2 gallons of DEF in 500 miles is not a confused tank level system, it’s an over usage and a major problem!!! I typically get a little better than the 2000 miles between fills.
How many miles on the truck and hopefully it is still under warranty. I would be taking it back to the dealer as quickly as possible.
How many miles on the truck and hopefully it is still under warranty. I would be taking it back to the dealer as quickly as possible.
Mountain Pass
Joined: Jul 2018
Posts: 137
Likes: 29
From: Northern MN
Urea gets injected into the exhaust based on a NOx sensor in the tailpipe. Higher NOx means more urea gets sprayed in.
Higher NOx is caused by the engine running at a higher temperature - so if you're pulling through the mountains you're going to use more urea than if you're on flat ground. It's supposed to be used at a rate between 2 and 6% of the rate you're burning diesel fuel at, so between 20 and 60 gallons of urea per 1000 gallons of diesel fuel.
So, your minimum possible is 2% for 500 miles, and if a gallon was 2%, then the total was 100 gallons or 5 MPG
The maximum possible usage is 300% more, or 6% for 500 miles, and if a gallon is 6%, then the total was 33 1/3 gallons, or 15 MPG
So if your actual MPG was between 5 and 15 MPG, it would not be out of range for your truck to burn 2 gallons of DEF, especially if you were pulling a heavy load or steep hills and causing engine temps to rise.
I love how they call it "DEF" to try and hide that it's basically filtered cow urine mixed with water (32.5% "industrial urea" and 67.5% de-ionized water)
Higher NOx is caused by the engine running at a higher temperature - so if you're pulling through the mountains you're going to use more urea than if you're on flat ground. It's supposed to be used at a rate between 2 and 6% of the rate you're burning diesel fuel at, so between 20 and 60 gallons of urea per 1000 gallons of diesel fuel.
So, your minimum possible is 2% for 500 miles, and if a gallon was 2%, then the total was 100 gallons or 5 MPG
The maximum possible usage is 300% more, or 6% for 500 miles, and if a gallon is 6%, then the total was 33 1/3 gallons, or 15 MPG
So if your actual MPG was between 5 and 15 MPG, it would not be out of range for your truck to burn 2 gallons of DEF, especially if you were pulling a heavy load or steep hills and causing engine temps to rise.
I love how they call it "DEF" to try and hide that it's basically filtered cow urine mixed with water (32.5% "industrial urea" and 67.5% de-ionized water)
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