# What happens with urea during extended storage?



## finnbmw (Jul 6, 2008)

I recall reading somewhere that the urea we are using in our diesels will crystallize over time. Is this true? If so, wondering what will happen with the system if the car is left sitting for a prolonged period? Will the urea crystallize in the lines, filter etc. and cause damage when the engine starts back up?

Just curious...


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## Snipe656 (Oct 22, 2009)

It has a shelf life of well over a year if I remember right. It does not crystallize due to age but instead seems to be because of temperatures. When too old it looses it's efficiency. Your fuel will probably get algae growth long before the DEF becomes an issue from sitting for prolonged periods of time. You'd still be talking about extremely long periods of time of sitting for the fuel to be a worry.


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## F32Fleet (Jul 14, 2010)

Evaporates and leavs crystal behind. IIRC 2 yr storage life so it should be a none issue.


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## Snipe656 (Oct 22, 2009)

In my experience fuel normally gets growth in it before 2 years so that would be my bigger worry if I were to have any worries about sitting. I could not imagine though having such a new car and leaving it collecting dust for so long.


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## bimmerdiesel (Jul 9, 2010)

I left my car in garage for 1 month and it started just fine and no issues. This was in Nov month with temps in 20-30F. And I am currently away for 7 weeks and left car in parking. Hopefully I will have no issues after these 7 weeks.


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## Snipe656 (Oct 22, 2009)

bimmerdiesel said:


> I left my car in garage for 1 month and it started just fine and no issues. This was in Nov month with temps in 20-30F. And I am currently away for 7 weeks and left car in parking. Hopefully I will have no issues after these 7 weeks.


My car has sat for months on end and I have had zero issues with DEF crystallizing. I of course do not live in a very cold environment either so take it for what it is worth. I am more worried about my battery holding enough charge through the long periods of sitting than anything else on the car.


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## UncleJ (May 7, 2006)

I think I would worry about the car stored for a long period in a hot environment which would hasten the evaporation of the urea solution in the lines and perhaps cause crystallization and clog the smaller orifices in the system. The urea system is a fairly new and I suspect that we will have much to learn about it as the years pass.:angel:


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## Snipe656 (Oct 22, 2009)

But what is a "long period" in days?


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## UncleJ (May 7, 2006)

6 months would be a "long period" IMHO.:thumbup:


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## ericwarren (Dec 11, 2004)

My car was on the lot for about 18 months before I purchased it
Have put on about 700 miles and all seems ok.
Should I have it drained and refilled??


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## UncleJ (May 7, 2006)

I doubt that it just sat in storage for 18 months. Almost certainly it was moved around the lot, if only to be washed, started frequently (to keep the battery up) and not shunted off into a dark corner to be forgotten.:angel:


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## GreekboyD (Jan 25, 2012)

ericwarren said:


> My car was on the lot for about 18 months before I purchased it
> Have put on about 700 miles and all seems ok.
> Should I have it drained and refilled??


Hard to say. I bought my 2009 BMW 335d with only 3,800 kms on it last August. About 2-3 days later I had the SES light come on and the SA said it was due to old urea sitting in the car and hadn't been changed for over two years. Fault code showed a clogged/hardened urea valve.

With 700 miles on yours though, I'd say you should be fine.


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## ericwarren (Dec 11, 2004)

i'll let the onboard computer be my guide then!
thanks.
e


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## Snipe656 (Oct 22, 2009)

My car sat outside for almost a year prior to being purchased but that was in Texas so not like it saw much cold weather. Now one that sat outside in Canada for such a period or longer then I'd be wondering about the transfer pump.


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