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Based on what I've read in the past, I would be inclined to also suspect the DEF system is overdosing.... but this should be easily confirmed and\or dismissed if you compare your DEF usage with the rest of us.... if you have accelerated usage, it's more than likely overdosing and leaving DEF cocaine all over your @$$
 

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Interesting. I wasn’t aware that urea in a sealed contains could degrade. Perhaps oxidize. I always thought it was essentially a salt. As apparently it’s break down is into ammonia.



As to 20K Miles? How many fills of the DEF tank is that?
 

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Extract from the manufacturer of the solution:
Consumption of AdBlue® depends on the vehicle weight and on individual driving style. On average a passenger car will consume about one and a half litres over 1000 kilometres.

Extract from '14 manual
AdBlue information
􀂤 Please first read and note the introductory information and heed the WARNINGS
In vehicles with selective catalytic reduction, a special urea solution (AdBlue) is injected into the
exhaust system ahead of the catalytic converter in order to reduce nitrogen oxide emissions.
AdBlue is stored in a separate tank of the vehicle and should be refilled under normal driving
conditions during service according to the maintenance schedule. The AdBlue tank holds slightly less
than 5 gallons (20 liters).
AdBlue consumption depends on the individual driving style, system operating temperature, and
outside air temperature. Therefore in rare cases AdBlue may have to be refilled between service
events.
Starting with a remaining range of about 1500 miles (2400 km), a reminder to refill AdBlue is displayed
in the instrument cluster ⇒ Refilling AdBlue. If you ignore the last refill reminder, it is impossible to
start the engine again after it is switched off ⇒ Warning and indicator lights.
Volkswagen recommends that you have the AdBlue tank refilled by an authorized Volkswagen dealer
or an authorized Volkswagen Service Facility. If no authorized Volkswagen dealer or authorized
Volkswagen Service Facility or other qualified workshop is available, you should refill at least 1.5
gallons (5.7 liters) of AdBlue (3 AdBlue bottles). Refill only the type of AdBlue that Volkswagen has
explicitly approved for your vehicle.
If warning lights 􀁢 and 􀀾 both come on together, there is a malfunction. Volkswagen recommends
that you take the vehicle to the closest qualified workshop.
AdBlue® is a registered trademark of the German Association of the Automotive Industry (VDA) in the
United States, Germany, the European Union and in other countries.
In my personal experience, I get flagged by the MFD in about 10k mi.
 

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Interesting. I get a 1,000 mile warning at around 3K miles. I have a ‘13 with the Def tank under the spare tire (3 gallon??). As I understand in ‘15 they added a full port next to the fuel filler. And on Audi Q7 they have a second tank for increased capacity (not sure if Touareg got this).
 

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I would say that's BEYOND excessive. There's a massive difference between my 10k and your 3k interval. Your system is clearly over-dosing for whatever reason.

Make sure you don't use expired DEF... it has a shelf life... can't recall what it is now... (doubt you'd have this problem since your Touareg drinks the stuff)
 

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I would say that's BEYOND excessive. There's a massive difference between my 10k and your 3k interval. Your system is clearly over-dosing for whatever reason.
Even if we take into consideration the fix potential increased usage as per
Diesel Exhaust Fluid (DEF) consumption - DEF (also known as AdBlue®) consumption for your vehicle may change. Some vehicles may experience an increase of 40% on average. The exact amount of the change will vary depending on driving style and other factors. This means some drivers will need to refill the DEF tank more frequently.
..... you should still be able around 6.5-7k intervals if your stuff is working as it should be.
 

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I pretty much always make it to 10k miles on a tank of Def. One oil change.
 

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Discussion Starter #30
My comment was directed at someone else......

Regardless, you have sufficient milage that it's quite feasible that your DPF may be approaching the end of its life (lots of contributing factors).... if you're not noticing a performance degradation, I would just ignore it and simply deal with the "cleaning" aspect of it... you could try a different brand of fuel, or maybe even DEF fluid, to see if anything changes.

What are your driving patterns like?
Do you drive like a granny?
What kind of climate do you drive in?
I am living in NC, so hot in summer.
I got a ticket for speeding 95 on 65, that was in early May. I chickened out after that and always set 74 cruise on my 250 miles commute once a week. The residue was happened after that.

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After diesel fix, I think it only last about 5000 miles?

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Read the posts above. If the original range was 10k and the fix increase was expected to be +40%, do the math. Keep in mind that both myself and others are also fixed, and we are still way above what you or NTDI are seeing....

You guys have much more increased usage.
 

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I've noticed the same thing on my 2015 Cayenne Diesel. White crusty inside the tailpipe. I never noticed it before - but never noticing it doesn't necessarily mean it wasn't doing it. Just never noticed it. Normally I notice this stuff during a hand wash of the car - but I haven't hand washed my Cayenne at all this year (just use the freebie wash at the dealer). I suspect this is a result of the latest software fix?

Talking to some friends who are still in the diesel engine industry - suggested it might be what's called "Ammonia Slip". Basically the Urea is injected, but they inject too much, or the throttle gets dropped suddenly while the urea is injecting - and not all the urea gets "used". What you wind up with is actual ammonia coming out the tailpipe. There are strict regulations around this because ammonia is pretty damned toxic.... makes me wonder if this is a mis-calibration with the latest "fixed fix" software.
 

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I pretty much always make it to 10k miles on a tank of Def. One oil change.
That's the intent as far as the system was designed.
After diesel fix, I think it only last about 5000 miles?

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The official oil change interval on the Cayenne Diesel is 5,000 miles (which is funny since it's the same damned vehicle.) A lot of us in the Cayenne Diesel circles always wondered how the T-reg/Q7 made it 10k on an Adblue fill after the dieselgate fix was applied....
 

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Pre-fix, my 2014 would make it over 10k miles between DEF fils. Post fix it dropped down to about 8k - same driving patterns. I never noticed any white residue at any point (RIP - totaled by a deer so I no longer have it). I towed with it (boat), i drove short trips with it and plenty of longer trips too.

Pre-fix I filled my own DEF one time (before they were free) and did notice some crystals around the top of the DEF filler, but they were larger crystals. I'm with the consensus that the white powder is ammonia residue (anhydrous ammonia is white), and that there is an issue with too much being injected (for whatever reason).

Coolant leaks produce white smoke but I've never seen white residue like that. Plus if it was coolant, i would expect that there would be other issues.
 
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@ ameoba
Your pre & post fix experience is directly inline with my claims above, and normal as far as I'm concerned......
 
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