I came across this site that might come in handy that shows retail locations, besides Walmart and the parts stores, for the diesel exhaust fluid. It would make it easier to get a fill If the pump has an auto-cut-off.

http://www.discoverdef.com/

 

I have been reading a forum on the Jeep GC diesel. Some owners try to go cheap on the Ad Blue fluid and get an "incorrect ad blue" warning light. I am very careful with this item because it seems that its shelf life is very specific. I would just pay a bit more for the OEM product and even then, check the expiration date.

 

Just like your engine oil, as long as it meets the specs that Porsche/VAG outline then you should be gold.

As far as the shelf life, there seems to be a lot of debate about that and it is almost as hot as your average engine oil debate.

From what I can tell it does not turn into a pumpkin at a specific time and I'm not convinced that it degrades appreciably over time. It can sit in your tank for a year or more (depending on you driving habits) and as you are never getting the tank bone dry, you're always mixing fresh in with old (especially if you're toping up at OCIs or some other frequent interval).

What I put far more credence in is how it is stored and transferred. It appears to like to be kept cool and dark and you don't want any contaminates to get into it. So don't buy the bottle that has been sitting in the front window or something like that and make sure you take care to clean the area and filling devices before you dump it in.

Much like carbonated water, the DEF will just stay liquid and "inert" if nothing molests it. As soon as it gets some contamination in it, however, it will start crystalizing and that is where your trouble really is.

We each have our own tolerances and risks we are willing to take though, and that's OK. For me the added cost of getting 5 gallons from the Porsche dealer vs the generic BlueDEF for a 3rd of the price is not worth it, but then I'm not willing to pay them $400 for an OCI either...

For me I bought a small branded bottle a couple months after I got the CD and would carry it on long trips just incase I got caught out. I finally dumped it in after it had been in my basement for a year. I then topped it off with BlueDEF and poured the remainder into the "crush" bottle to again use as an emergency backup. That was 8 months ago and I check on the bottle (again in my basement when not road tripping) and there are no signs of crystallization or anything else that would cause me not to dump it in the tank when needed.

 

The jeep problems were due to DEF crystals clogging the sensor. The Cayenne diesel sensor cannot analyze the DEF for quality or age, it is just a level indicator like the fuel gauge since there are no proprietary additives for it.

If emission testing is a concern then having fresh adblue should help pass. The 5000 mile DEF service/oil changes are more of a function to keep the DEF working as per specs since there are light and temperature variables that could adversely affect the product.