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Old 07-07-2018, 09:39 PM   #1
Brand: Thor Motor Coach
Model: Palazzo 36.1
State: Texas
Posts: 32
THOR #3182
DEF at the pump?

After having to take our coach in for a check engine light on a 6.7l ISL I asked what could have caused the NOX sensor issue and the service tech asked if I filled up at the bulk DEF pumps or used jugs.
I use the pump when it's available and he advised me to use jugs to possibly avoid this problem in the future.
He said it could have been the DEF sits in your motorhome longer than it does on most of the trucks that buy at the pump so it doesn't have a chance to go bad.
It did make sense but, does DEF really go bad if it sits for a few months? I never heard that before.

It turned out the repair was emissions related so, it didn't cost us anything since we're only at 16K miles but if anyone's ever heard of this I'll certainly stay away from the DEF at the pump. Some of these truck stop pumps are sketchy I must say, there's no telling what could be in the tanks.

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Old 07-07-2018, 10:11 PM   #2
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Brand: Thor Motor Coach
Model: 2017 Windsport 29M
State: Indiana
Posts: 3,691
THOR #5196
Since not all trucks use DEF there is no way of telling how been sitting in the tanks.

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Old 07-07-2018, 10:32 PM   #3
Senior Member
Brand: DRV
Model: 41RSSB4
State: South Dakota
Posts: 270
THOR #5859
Sounds to me like the typical "its his fault" syndrome we suffer from today.
How long do they think the DEF stays on a shelf at a store that sells DEF?
Really stupid answer in my book. We never know how long anything has been in the tanks. Fuel or milk. Dosnt mean its bad. If a truck stop is sketchy why stop there? Is the fuel any better than the DEF?
Yankton, SD for the summer.
2015 Mobile Suites 41RSSB4
2011 F350 Dually 6.7 PSD
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Old 07-07-2018, 10:57 PM   #4
Junior Member
Brand: Thor Motor Coach
Model: Venetian M37
State: Texas
Posts: 25
THOR #10920
DEF has a shelf life. Boxed DEF has a month/date label. Shelf life is dependent upon temperature stored.... the higher the temperature the shorter the life. You should be able to search internet and find out shelf life vs. temperature. Considered it a problem in early on travels, but have not worried too much about it lately. Always run DEF tank to near empty before refilling on first outing. My trips are annual with long trips when we go out. Have used bulk DEF with no problems, but you just don't know it's age.
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Old 09-02-2018, 02:37 AM   #5
Senior Member
Brand: Thor Motor Coach
State: Ohio
Posts: 148
THOR #12726
yes def does have a shelf life, but there are so many vehicle using it that I doubt if old def caused the issue, having said that ,my job at work is soley diagnosing and repairing cummins and Detroit aftertreatment systems and most time the problem is with the wiring as freightliner as several issue's of wiring harness being pulled to tight and rubbing through and yes nox sensors do act up by drifting high or low called an in-range nox drift
when that happens the systems gets knocked of balance as the inlet nox must be reduced by 80% if either nox sensor is off by more then 10% then it starts throughing nox conversion codes and can slightly derate to 55mph and next step is called a scr driver induce derate which limits the vehicle to 5mph and kicks on the red stop light, unfortunly they are about 500-600 dollars to replace but ,they can run a scr test to see if both sensors read within 5ppm of each other
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Old 09-02-2018, 11:40 AM   #6
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Brand: Thor Motor Coach
Model: Axis 24.1
State: Michigan
Posts: 8,654
THOR #1150
I was a little surprised to see BlueDEF at Home Depot yesterday. They had a big stack of boxes of it.

Just pointing it out--if you already knew then move along LOL.
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Old 09-02-2018, 12:52 PM   #7
Thor Palazzo 33.3 diesel
TurnerFam's Avatar
Brand: Thor Motor Coach
Model: Palazzo 33.3 34'bunkhouse
State: Georgia
Posts: 2,297
THOR #4735
the stories and concerns of DEF going 'bad' while in your tank is probably overkill, as with many other 'rv' related stories. We've used the W*mrt 2 1/2 gal jugs for over 4 years now, and have never had any issues, and yes, our coach has sat for 'months' during the winter with no issues.
I actually have only used the 'pumps' once, then realizing that it's just much easier and simpler to carry my own jug, and pick up another at the next big box store. No issues.
If it makes you feel better, when you purchase the jugs, check the seal under the cap to make sure it's fully intact.

the Turners
'14 Palazzo 33.3 bunkhouse 34' diesel
KingTailgater2 Dish HD, 100w/5a SOLAR, BlueOx
100,000+mi since '14 - US, Alaska, Canada - Hiawassee, GA! (also, '14 Gulfstream Amerilite and '07 ForestRiver Rockwood) : )
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