The Five Star DEF Story: The Search for the Facts Begins

While in sunny Florida, we began to research Diesel Exhaust Fluid: What it is, how it’s made, and how it works in our F350. We had already discovered that The International Standards Organization (ISO) is the source of governing documentation for DEF.

Diesel Exhaust Fluid (DEF is the acronym) is also known as Aqueous Urea Solution (AUS) 32. The governing specification for DEF is ISO22241 with a revision level of 2006. The ISO 22241 series provides the specifications for quality, storage, refilling interface, and test methods for DEF. ISO 22241 is titled “Diesel Engines – NOx Reduction Agent AUS32” and consists of the following parts and associated release dates:

  • Part 1: ISO22241-1:2006 Quality Requirements
  • Part 2: ISO22241-2:2006 Test Methods
  • Part 3: ISO22241-3:2008 Handling, Transportation, and Storage
  • Part 4: ISO22241-4:2009 Refilling interface (applies to commercial vehicles and buses as defined in ISO 3833)
  • Part 5: ISO22241-5:2009 Refilling interface for passenger cars

These ISO standards (and other that they reference) are the authoritative documents for DEF. Period. If you use DEF that meets these requirements, you are using the DEF recommended for your vehicle.*

ISO specifications are only available by purchasing them, and cannot be reproduced or duplicated in any way. They are also expensive, but we already had decide that we were going to find, and possible sell, a better DEF solution. So we bought parts 1, 2, and 3. Total price: $320.00 including the ISO specification for “Water for analytical laboratory use - Specification and test methods”, ISO3696:1987” that is referenced in Part 1 of ISO22241-1. What is revealed in these documents is the foundation for Five Star DEF; I’ll go into more detail in the next part of this blog.

*What about API certification? I’ll provide a detailed discussion on this topic soon, but the simple fact is that API Diesel Exhaust Fluid Certification is voluntary. See

7 comments (Add your own)

1. Julio wrote:
Eciomnoes are in dire straits, but I can count on this!

Wed, July 1, 2015 @ 12:38 AM

2. wrote:
I have read so many articles concerning the blogger lovers however this article is really a good piece of writing, keep it up.

Thu, June 6, 2019 @ 4:55 AM

3. Ugozed wrote:
levitra generic

Tue, October 15, 2019 @ 1:31 AM

4. Ashzed wrote:
levitra generic

Tue, October 15, 2019 @ 6:35 AM

5. Boozed wrote:
levitra generic

Tue, October 15, 2019 @ 1:20 PM

6. Wimzed wrote:
[url=]buy levitra online canada[/url]

Tue, October 15, 2019 @ 8:48 PM

7. wrote:
Greetings! Very helpful advice in this particular article!
It's the little changes that will make the most important changes.

Thanks a lot for sharing!

Mon, March 30, 2020 @ 12:46 PM

Add a New Comment


Comment Guidelines: No HTML is allowed. Off-topic or inappropriate comments will be edited or deleted. Thanks.