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Old 09-29-2020, 09:40 PM   #1
Senior Member
Join Date: Aug 2013
Location: Sherwood, Arkansas
Posts: 151
Def or aging

I am fairly new to DP motorhomes.

What is the life of DEF before it is not effective? I have not used the motorhome much this year and am wondering if I need to drain the tank and replace with new.
James and Teresa,
DW of 32 Years.
2014 Coachmen Sportscoach Cross Country 360DL

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Old 09-29-2020, 10:15 PM   #2
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Join Date: Aug 2019
Posts: 1,060
call peaks def help desk.
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Old 09-29-2020, 10:47 PM   #3
Join Date: Apr 2018
Location: Canada/Australia
Posts: 94
The life of DEF is dependent on ambient temperatures, the warmer it is the shorter the life span of DEF. Each container of DEF has a manufactured or bottled date on it, and just to make your life harder just about each manufacturer has their own coding system to assist you in deciphering the date, you can research each manufacturer, as I did and create a list of each type you use or find in your normal travels, create a word doc print it and store it in your glove box for use or just buy from somewhere like flying J that the DEF doesn't sit in their tank or on the shelf for long periods. Basically the standard I use is 1 year, now I live in Canada and we have hot summer but long cold winters, so in my case if the DEF has been in longer than 1 year I removed the filler tube going into my DEF tank and pump out the old DEF. I may be overly concerned about the age of my DEF as I only put about 5K on my truck a year, so it's not abnormal to have 1 year old DEF in my truck, and I have been told the cost to repair a DEF system that the DEF has been allowed to crystalize in is around $11K CDN. To each their own but a little maintenance now is a lot cheaper than a repair later on. As my truck is currently in storage for three years since I live outside of Canada (job) my truck goes to RAM twice a year once in the spring and once in the fall to have the DEF removed and replaced (1 Gallon) no need to fill it as is only coming out in 6 months.
"Never forget the journey is as important as the destination"

2014 Ram 3500 Laramie 4X4 CTD
2011 Dutchmen Denali 262 RLX
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Old 09-30-2020, 08:10 AM   #4
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Join Date: Mar 2020
Posts: 72
I have the same concern, a process I use that works for me is I don’t fill up DEF to full. I always carry a 2.5 gallon DEF jug, when it get to half a tank I buy another DEF ( so I never am with out a spare DEF) put the older one in, which will fill it to 3/4 full. Not a full timer but I think this helps maintaining fresh DEF with 1/4 tank to spare if I need to put in a fresh jug after storage.

Not the most cost effective but with as little as it uses it is very convenient to put it in at home on my schedule and not worry about getting it at truck stops.
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