This topic is coming up more and more often and the answer is somewhat complicated since the answer lies within the definition of what is Diesel Exhaust Fluid. In order for something to be called a Diesel Exhaust Fluid (DEF) the product must meet the following criteria:
Must meet ISO 22241—Which is an international standard that defines the quality requirements for DEF including production, storage and distribution. The production, handling and transportation of DEF is governed by the ISO 22241 standards. The key points are:
Diesel Exhaust Fluid (DEF) must have a urea concentration of 32.5% by weight. This concentration was chosen because it is has the lowest freezing temperature, 12°F.
The maximum level of impurities such as calcium and various metals such as iron, copper, zinc and aluminum are clearly specified. These limits are extremely low, to ensure reliable operation of the SCR system.
This definition excludes the use of urea grades used in agriculture, and requires water purified by distillation or deionization or similar.
IF a product does not adhere to the ISO 22241 standards, then that fluid cannot by definition be called a Diesel Exhaust Fluid (DEF). With a growing market there will be more and more unlicensed products to hit the streets calling their product DEF but it will simply be a urea solution. The only reason why a product would be unlicensed would likely be that it wouldn’t meet the ISO and API standard for DEF. The issue with these products will be that they will likely lead to failures of SCR systems. Some of these failures could be immediate and others will likely take days, weeks, months or even years to detect before leading to a failure, but premature failure of the SCR system will occur.

Even today there is a lot of discussion on blogs talking about how even some independent blenders of DEF who have registered with the API and follow the ISO 22241standards are not testing every batch and that some batches are not meeting the very strict ISO 22241 standards.


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This can happen for a number of reasons, but primarily due to the type and purity of urea is not the Pharmaceutical Grade Urea but rather the Agricultural Grade Urea which contains impurities like aldehydes and excessive levels of biuret in relation to the ISO 22241 standards which are poisonous to the SCR systems. The other area that will cause critical failures for the manufacturing of DEF is the water purity. De-Ionized water is critical to the manufacturing of DEF. The slightest amount of metals/contaminants found in the water will cause the fluid to not meet the ISO 22241 specification and these elements will be poisonous to the SCR system. Elements like:
Calcium, Zinc, Magnesium, Iron, Chromium, Nickel, Sodium and Potassium
All of the above are found in varying quantities/concentrations in typical tap water.
In closing, ONLY product that adheres to the ISO 22241 specification and is licensed with the API can be called Diesel Exhaust Fluid...all other products are simply Urea Solutions to various concentrations and cannot be called Diesel Exhaust Fluid.

Take it one step further and ONLY those suppliers who have long term supply arrangements with the producers of Urea and more specifically Pharmaceutical Grade Urea will be in a position to keep the market supplied with Diesel Exhaust Fluid so picking the right Supplier and Distributor is essential to ensuring that you have product to keep your fleet and equipment moving.


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