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Hello all,

I am not sure how many of you are aware of this. DEF has a maximum shelf life of approximately 2 years under ideal circumstances. DEF will degrade over time and if introduced to our CTD, could cause multiple DTCs to set. So the burning questions becomes, how do I identify the manufacture date of my DEF fluid?

I can only speak to Peak Blue DEF, however, I suspect others may use the same manufacturing code process. Peak uses a standard ISO date code. Here is how to decode on the 11 digit number stamped on the container:

Digits:
1-2 = Manufacturing Facility
3-4 = Manufacturing Year + 1
5-7 = Days left in the manufacturing calendar year
8-11 = Batch Code

So here is the code stamped on a jug of DEF I purchased at my local Wally-World:

PB182443314 (found on side of container and also on the box)

PB = Manufacturing Facility
18 = 2017 (remember, 18-1=17)
244 = May 1 (244 days left in 2017)
3314 = Batch code

DEF Tips:

Always try to purchase the newest DEF you can find. DEF should never be stored in direct sunlight or at temperatures above 80 degrees for an extended period of time. If either of these conditions occur, the shelf life will be reduced.

So the next question I can hear is "I live in Phoenix", it is rarely below 80 degrees. My answer to that is simple. Only add enough DEF to your CTD to get you by (2.5 gallons) and then let it run low and add more. I would not suggest filling the tank with 4.9/4.6 gallons, especially if you do not drive in a way to consume the DEF rapidly. It took me 15K miles to go through a full tank of DEF. That was over 6 months. Because I am heading into summer, I only added 2.5 gallons. I will add more in the fall or when requested by my CTD.

Bottom line, check you DEF date codes and buyer beware! I hope this helps someone.

:eek:ccasion14:
:usa:
 

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Also purchase from a local truck stop that has it at the pumps. It is always a fresh supply and the tanks are underground where the temp is cooler. Not to mention it is easier to dispense and is lesser in cost. I have noticed more places are getting it installed at the pumps.

You can search here.
 

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I did score 2 gallons of Blue DEF that was on clearance at Walmart for .50 a gallon. I took a chance and grabbed it. Turns out I was down exactly 2 gallons because that filled my tank. Been over a month now and no issues. Didn't check the date code.
 

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What exactly goes bad with DEF which is basically ammonia? I agree buy the freshest possible just because it makes sense. Does old DEF harm the sensors or give false reading to the sensors? DEF never enters the engine, it is simply injected into the exhaust to make a CTD...a CTD.
 

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What exactly goes bad with DEF which is basically ammonia? I agree buy the freshest possible just because it makes sense. Does old DEF harm the sensors or give false reading to the sensors? DEF never enters the engine, it is simply injected into the exhaust to make a CTD...a CTD.
def exposed to air crystallizes, keeping the reservoir less than full adds to crystallization, crystals equal issues, clogs...

the sensors read the differential pre and post def injection, if readings are off, def gets blamed...but its always the sensors gone bad, or not enough/too much being injected
 

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DEF does expire, and it will cause issues if it is bad. It's unlikely, but possible. Most of it has a date on the bottle, I know the ACDelco does. That's what I use in my car because I am anal retentive
 

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I still don't know how to read expiration date on ACDelco.
1) Printed on back label: 042621A
The following code is print on bottom of ACDelco 1-gal, DEF fluid.
00690405211519-4
This longer code does not match the date analysis in the above post.

If anyone knows how to 'de-code' and get mfg. date, please post and let me know.
Thanks,
bestLen
 

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I got lucky with this. Early in my CTD life I 'stocked up' and bought like 2 or 3 jugs of DEF that I didn't need. Thankfully I didn't have problems with them since it was over winter and I put a ton of miles on my car so I used it within a year.
 

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DEF technically doesn't expire or go bad if it is not opened and introduced to atmosphere.

What happens is it loses its water content and that changes its urea to water ratio. Storage should always be in a cool place.

As long as it is clear and not cloudy it will be fine.

Best practice is to keep a clear jug and buy it at a truck stop that has a lot truck traffic as others have said although most probably just buy it at a local store and that works also.

Me I keep my def full not letting it get lower than a gallon with the intent of keeping the heater always submerged. I have a theory these heaters fail when people wait for the def low message to come on. Just a theory and I'll see if my heater goes the distance or gives me the dreaded count down at some point.
 

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DEF technically doesn't expire or go bad if it is not opened and introduced to atmosphere.

What happens is it loses its water content and that changes its urea to water ratio. Storage should always be in a cool place.

As long as it is clear and not cloudy it will be fine.

Best practice is to keep a clear jug and buy it at a truck stop that has a lot truck traffic as others have said although most probably just buy it at a local store and that works also.

Me I keep my def full not letting it get lower than a gallon with the intent of keeping the heater always submerged. I have a theory these heaters fail when people wait for the def low message to come on. Just a theory and I'll see if my heater goes the distance or gives me the dreaded count down at some point.
It breakdowns into ammonia… Which just goes into the solution. This is actually better for SCR.

But it does affect the refractive index which is what the ECM uses to detect bad DEF. It has to be pretty bad for this to happen. Like you let it sit in direct sunlight when it’s 140 degrees.

Needless to say… Stored in a cool dark place…. DEF will outlive you, your kids, and their kids.
 

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I usually buy 2-3 jugs at a time (cut down to two now that we don't drive nearly as much) and store it in my basement, so that should be the optimal place for it (since it sits at like 70 all the time and isn't damp).
 
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It breakdowns into ammonia… Which just goes into the solution. This is actually better for SCR.

But it does affect the refractive index which is what the ECM uses to detect bad DEF. It has to be pretty bad for this to happen. Like you let it sit in direct sunlight when it’s 140 degrees.

Needless to say… Stored in a cool dark place…. DEF will outlive you, your kids, and their kids.
True, it does, but it takes heat to make it ammonia
 
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