WHEN TO ADD DEF FLUID???
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Freshman User
Joined: May 2012
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WHEN TO ADD DEF FLUID???
Hi, Well I am getting more confused by the day. It seems that there is 2 thoughts as to when you should add DEF fluid.
My truck is only a few months old. I have never added fluid yet. I am slightly under the half full mark. I was going to add a full jug which should bring the level up to almost full. I figured no harm.
Now I am hearing that you should ONLY add when the :Add DEF fluid" comes on because of the way the tank senses level, or something like that?? Huh?
Sorry if this has been asked before. I would love to hear your thoughts!
Thanks, Shaun
2019, F350 King Ranch
- When the "Add DEF fluid" notification comes on.
- Anytime you want prior to running completely out.
My truck is only a few months old. I have never added fluid yet. I am slightly under the half full mark. I was going to add a full jug which should bring the level up to almost full. I figured no harm.
Now I am hearing that you should ONLY add when the :Add DEF fluid" comes on because of the way the tank senses level, or something like that?? Huh?
Sorry if this has been asked before. I would love to hear your thoughts!
Thanks, Shaun
2019, F350 King Ranch
Post Fiend
Joined: Nov 2001
Posts: 6,748
Likes: 118
From: Tallassee, ALabama
I add it at different times. If no trips planned.I wait for the 500 miles notice or if I check and it is below half full. If going on a trip, I top off the tank and carry a spare container.
I have never had any issues with the DEF system and it not resetting if I add before the 500 mile notice.
I use the Ford PM-27N nozzle to fill the tank. It stops the flow without spilling DEF all over the truck if overflow.
I have never had any issues with the DEF system and it not resetting if I add before the 500 mile notice.
I use the Ford PM-27N nozzle to fill the tank. It stops the flow without spilling DEF all over the truck if overflow.
Posting Guru
Joined: May 2019
Posts: 1,643
Likes: 14
From: Central Ky.
I add it at different times. If no trips planned.I wait for the 500 miles notice or if I check and it is below half full. If going on a trip, I top off the tank and carry a spare container.
I have never had any issues with the DEF system and it not resetting if I add before the 500 mile notice.
I use the Ford PM-27N nozzle to fill the tank. It stops the flow without spilling DEF all over the truck if overflow.
I have never had any issues with the DEF system and it not resetting if I add before the 500 mile notice.
I use the Ford PM-27N nozzle to fill the tank. It stops the flow without spilling DEF all over the truck if overflow.
and that Ford filler nozzle works great too!
More Turbo
Joined: Dec 2018
Posts: 535
Likes: 23
From: Arkansas
I add when the deal tells me I have 500 miles to empty, last time I forgot it was a 5 gallon tank and only bought 1-2.5 gallon jug, will run it down again and add when it tells me to again. being as you have a the ability to tell if it's at half, etc. you must have a newer truck, I cannot tell you if they suffer the same issues that some of the prior superduty's do with filling too frequently, etc.
Cargo Master
Joined: Feb 2015
Posts: 2,338
Likes: 255
From: Livermore Ca.
When I add DEF when the thing says I'm below 1/2 it's always been a lie. It never takes a full box. Just wait till the truck tells you to add it. The 500 miles till limp will go away before limp mode./ You can't reset this. I know I tried. I was super nervous the first time but the message went away on it's own.
At first i carried a box with mo on a trip but you don't have to. There is a Walmart on every corner. You can find DEF all over the place.
At first i carried a box with mo on a trip but you don't have to. There is a Walmart on every corner. You can find DEF all over the place.
Hotshot
Joined: Oct 2015
Posts: 19,676
Likes: 12,797
From: Wyoming
There seems to be differences between pre-2017 and 2017+ DEF systems. On the older systems, waiting for the notice seemed to work and was necessary. Beats me why. On 2017+ there have been issues with the truck getting so low on DEF that it gets "stuck" on the 50 miles to empty warning even though you've added DEF. Not all trucks behave this way.
I wait for the gauge to get below the 1/2 mark and add one 2.5 gallon jug. I have never had to stop filling the tank. I use the entire jug. With this method I never have the warning come up and never have "DEF anxiety".
I wait for the gauge to get below the 1/2 mark and add one 2.5 gallon jug. I have never had to stop filling the tank. I use the entire jug. With this method I never have the warning come up and never have "DEF anxiety".
FTE Legend
Joined: Mar 2017
Posts: 31,760
Likes: 9,113
From: Western NY
I've done it both ways but never had a problem with keeping the DEF tank full on my 16 without seeing the 500 miles warning. I started to keep it full again to keep fluid on the heater which I remember someone on here saying to do to possibly help the heater from burning out. It said approximately 2.5 gallons every 3k to 4k miles.
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This is a little off topic but I got the DEF heater code on my 2011 Sprinter and couldn't justify $2000 to fix a problem that in reality is not a problem here in SC where it essentially NEVER gets as low as 12 degrees. Mercedes "makes" it a problem by keeping the check engine light on masking other potential problems that "share" the check engine light. Instead I bought a Mercedes specific OBD code scanner and used it periodically to be sure there was no REAL problem.
Anyway after about 2 years of that stupidity I got a screen display saying to add DEF fluid. (I've driven less than 30,000 miles in almost 10 years and the DEF fluid has always been added by the dealer when serviced so this was a first for me.) Due to my local auto parts stores not stocking more than a single one gallon DEF container I added 3 gallons over a time period of 5 days. (I didn't want to deal with the 2.5 gallon "boxes" of DEF). The third gallon turned off the screen display but to my surprise the next day I noticed the check engine light had turned OFF! So far it has remained off so the problem seems to have been fixed by adding DEF fluid.
My "theory" (perhaps someone familiar with where connections are located in the DEF heater wiring can comment on this) is that a connection in the DEF heater wiring - perhaps inside the DEF tank - developed enough resistance to be sensed as an open circuit DEF heater fault. Which persisted for almost 2 years keeping the check engine light ON. Then adding DEF fluid splashed enough of this corrosive liquid (DEF fluid) on that connection to reduce the resistance to a level that doesn't get detected as a fault.
Again, just MY theory but something has to explain a $2000 problem curing itself. So, on the outside chance it helps someone I'd suggest adding a small amount of DEF each day for several days - enough to splash on and possibly clean a corroded connection causing a DEF heater fault.
You MIGHT have to wait until your DEF fluid is low enough. I added 3 gallons over about 5 days. You may see no benefit but it's worth a shot since you will eventually need it anyway. My "hunch" is that adding a smaller amount over more days (more splashing inside the tank) MIGHT work even better but AGAIN it might not.
Anyway after about 2 years of that stupidity I got a screen display saying to add DEF fluid. (I've driven less than 30,000 miles in almost 10 years and the DEF fluid has always been added by the dealer when serviced so this was a first for me.) Due to my local auto parts stores not stocking more than a single one gallon DEF container I added 3 gallons over a time period of 5 days. (I didn't want to deal with the 2.5 gallon "boxes" of DEF). The third gallon turned off the screen display but to my surprise the next day I noticed the check engine light had turned OFF! So far it has remained off so the problem seems to have been fixed by adding DEF fluid.
My "theory" (perhaps someone familiar with where connections are located in the DEF heater wiring can comment on this) is that a connection in the DEF heater wiring - perhaps inside the DEF tank - developed enough resistance to be sensed as an open circuit DEF heater fault. Which persisted for almost 2 years keeping the check engine light ON. Then adding DEF fluid splashed enough of this corrosive liquid (DEF fluid) on that connection to reduce the resistance to a level that doesn't get detected as a fault.
Again, just MY theory but something has to explain a $2000 problem curing itself. So, on the outside chance it helps someone I'd suggest adding a small amount of DEF each day for several days - enough to splash on and possibly clean a corroded connection causing a DEF heater fault.
You MIGHT have to wait until your DEF fluid is low enough. I added 3 gallons over about 5 days. You may see no benefit but it's worth a shot since you will eventually need it anyway. My "hunch" is that adding a smaller amount over more days (more splashing inside the tank) MIGHT work even better but AGAIN it might not.
Cargo Master
Joined: Mar 2008
Posts: 2,975
Likes: 19
From: Archdale,N.C.
Hi, Well I am getting more confused by the day. It seems that there is 2 thoughts as to when you should add DEF fluid.
My truck is only a few months old. I have never added fluid yet. I am slightly under the half full mark. I was going to add a full jug which should bring the level up to almost full. I figured no harm.
Now I am hearing that you should ONLY add when the :Add DEF fluid" comes on because of the way the tank senses level, or something like that?? Huh?
Sorry if this has been asked before. I would love to hear your thoughts!
Thanks, Shaun
2019, F350 King Ranch
- When the "Add DEF fluid" notification comes on.
- Anytime you want prior to running completely out.
My truck is only a few months old. I have never added fluid yet. I am slightly under the half full mark. I was going to add a full jug which should bring the level up to almost full. I figured no harm.
Now I am hearing that you should ONLY add when the :Add DEF fluid" comes on because of the way the tank senses level, or something like that?? Huh?
Sorry if this has been asked before. I would love to hear your thoughts!
Thanks, Shaun
2019, F350 King Ranch
Lead Driver
Joined: Nov 2005
Posts: 5,212
Likes: 4,215
From: Kaysville Utah
I've had a 2011, A 2015 and now a 2017. I fill up whenever it's below 1/2 and I'm near a pump. I have not bought a bottle of DEF in years. If I'm getting fuel and their is a DEF pump on the island and I'm below half. I top off. Never had a problem
More Turbo
Joined: Dec 2018
Posts: 535
Likes: 23
From: Arkansas
I used to do the same thing with my pickups throughout the years, but being as I haven't yet been able to find a station with a DEF pump where I live, I'm back to buying the jugs, local Atwoods has a brand that meets spec and is only $5.99 for 2.5 gallons, cheaper than I've been able to find elsewhere, til it gives me issues it's what I'll use.
Senior User
Joined: Jan 2013
Posts: 238
Likes: 0
From: Northern New Mexico
There seems to be differences between pre-2017 and 2017+ DEF systems. On the older systems, waiting for the notice seemed to work and was necessary. Beats me why. On 2017+ there have been issues with the truck getting so low on DEF that it gets "stuck" on the 50 miles to empty warning even though you've added DEF. Not all trucks behave this way.
I wait for the gauge to get below the 1/2 mark and add one 2.5 gallon jug. I have never had to stop filling the tank. I use the entire jug. With this method I never have the warning come up and never have "DEF anxiety".
I wait for the gauge to get below the 1/2 mark and add one 2.5 gallon jug. I have never had to stop filling the tank. I use the entire jug. With this method I never have the warning come up and never have "DEF anxiety".
FTE Legend
Joined: Mar 2017
Posts: 31,760
Likes: 9,113
From: Western NY
I started with your method to fill my 2012. DEF less than half full .... add a 2.5 gallon jug and that worked fine. However, in the last year or so it has not taken the full jug and there has been a couple of cups left in the jug + some overflow. Need to get the Ford DEF nozzle and/or run it a couple of hundred miles after the 'less than half full' message but before the '500 mile' message then add a full jug.
Motorcraft PM27N Spout
Hotshot
Joined: Oct 2015
Posts: 19,676
Likes: 12,797
From: Wyoming
I started with your method to fill my 2012. DEF less than half full .... add a 2.5 gallon jug and that worked fine. However, in the last year or so it has not taken the full jug and there has been a couple of cups left in the jug + some overflow. Need to get the Ford DEF nozzle and/or run it a couple of hundred miles after the 'less than half full' message but before the '500 mile' message then add a full jug.
On my truck, at slightly below the 1/2 mark on the gauge my tank has about 3.7 gallons left (tank total capacity is 7.4 gallons). So a 2.5 gallon jug won't fill it up and it won't overflow. On the pre-2017 trucks the tank is 5 gallons, or so I read. So at 1/2 you have a good chance of filling up and overflowing the tank.