DEF - all the same?

DEF is manufactured to an international standard: ISO22241. I've purchased and read the specifications and DEF meeting the ISO standard contains "pure water" and "technically pure urea".

Pure water can me made using a variety of processes: Reverse Osmosis, distillation, and Ion-exchange filtration. The key is removal of anything that is not water.

Technically pure urea is usually made from natural gas in a very sophisticated and expensive chemical process facility with extensive controls for purity and content. Technically pure urea is somewhat similar to agricultural urea, but is much purer and contains no contaminants that could adversely affect the SCR system (like biuret). I've tested DEF made from both, and there are vastly more contaminants in agricultural urea.

I've purchased technically pure urea used for DEF manufacture, and have had it tested when dissolved in pure water. The resulting aqueous urea solution is very pure. Testing is quite expensive, about 600-800 dollars per test.

All DEF labeled ISO22241-1 is the same. Also look for the API certification mark on any container of DEF. This mark means that the manufacturer has registered their company with the API, submitted evidence of compliance with ISO 22241, and has paid the annual royalty fee of $7500 for the marking. The API conducts random sampling and testing of DEF to monitor DEF quality. The number of tests is small (less than 100 per year at this time). I met with the API employee that runs this program at the 2013 Diesel Exhaust Fluid Conference. The API seems committed to increasing quality monitoring.

Make sure DEF you buy in jugs is fresh (look for a date code). DEF shelf life is about 2 years at room temperature, less if stored above 90F. Make sure the seal is intact on any jug before using it. Bulk DEF from truck stops is usually fresh and is filtered in the dispensing equipment prior to going in your tank.

Use caution with filling gas cans or any containers with bulk DEF. There are very few materials that can be used in contact with DEF without contaminating the DEF. Avoid storing DEF in any container with metallic components that can easily contaminate the DEF. Plain rubber materials have poor compatibility with DEF. Plain steel containers would result in severe contamination of the DEF in a short time. Previously filled retail jugs may be usable, but are usually labeled for one-time use. Be careful reusing any cap with a paper-foil seal.

I'll try to answer any questions RV.net members have about DEF. I'm a semi-retired engineer and have made Clean Diesel technology a hobby of mine, and amassed quite a lot of information on the subject of Diesel Exhaust Fluid.

"Doctor DEF"

Great link. Thanks all for the info.

Here is a link to probably everything you ever wanted to know about DEF.

http://www.discoverdef.com/def-overview/

DEF is mandated by the Feds, and the specification is pretty specific. Urea is one of the cheapest chemicals available, and the only other ingredient is the distilled water in which it is dissolved. Pretty simple to make, pretty simple to test and pretty hard to screw up without bringing the Feds around to investigate. About the only two things that can go wrong is that it can be degraded by being too old and the clown adding it to the tank can get grease, dirt, or other contaminants in there. Other than that, pretty foolproof. Unlike the REST of the emissions system.

So, all DEF is supposed to be the same. Buy whatever you can find when you need it, and don't plan to store it for years in your trunk or garage. Fresh is the word.

When you get done pouring it in you throw the empty container in the campfire and stand up wind. Tree hugger baby, tree hugger all the way. :)

So far the only DEF I need is for the Ford 6.7 Diesel pickup, buy from Cummins at 2.5 gal @ $8.00.
about the same at truck stops that have it at the pumps.

Through the study that I have done DEF is DEF. However there is a shelf life on DEF so make sure that what you purchase has a recent code date on it. I believe that the life of DEF is a year. You can research that very easily. I have found Walmart's to be fresh. I would think that any big truck stop would have fresh product in their tank.

I think all DEF meets the same standard.

In our area, I've only found a couple of places to buy DEF. Walmart sells a 2.5 gallon box for about $12.00. The local auto dealers sell it too. If you can find a local truck stop that sells DEF, it's about $2.80-$3.00 gallon, much cheaper.

Since I don't have any truck stops locally, I'm forced to buy at Walmart. I carry a two 2.5 gallon DEF jugs in my RV so that when I find it at the pump I'll be able to fill my coach and have some extra.

Sooooo.....the answer to your question is that it should be all the same. There is a website called Five Star DEF that sells a powder version that you can mix with a gallon of distilled water in an emergency. They also sell jugs that are designed to be used for storing DEF and have a long flexible nozzle.