The way DEF functions is by turning NOx into innocuous nitrogen and water vapor. It enables diesel engines to comply with the Environmental Protection Agency’s (EPA) and the California Air Resources Board’s (CARB) stringent emissions rules.
All diesel vehicles and equipment with engines built after 2010 are required to use DEF in the United States. This includes semi trucks, pickups, buses, dump trucks, generators, agricultural equipment, mining equipment, and more. DEF has become an essential fluid for modern diesel engines to operate cleanly. Follow along this blog post by Azure Chemical to get the latest insights.
Contents
How Does DEF Work?
Diesel exhaust fluid (DEF) works by chemically reducing the oxides of nitrogen (NOx) in diesel exhaust into harmless nitrogen and water vapor.
DEF is injected into the vehicle’s exhaust stream and passes through a catalyst. The DEF breaks down into ammonia, which reacts with the NOx emissions. Specifically, the DEF converts nitrogen dioxide and nitrogen oxide into diatomic nitrogen and water vapor. This chemical reaction uses a process called selective catalytic reduction (SCR).
The SCR catalyst facilitates the reaction between the DEF and NOx compounds. As exhaust gases pass past the catalyst, the DEF effectively transforms the NOx into harmless byproducts before it is emitted from the tailpipe. As a result, diesel vehicles can now satisfy NOx emission regulations.
Without DEF, the SCR system would not function, and NOx emissions would be significantly higher. So, DEF is essential for modern diesel vehicles to reduce air pollution. The simple chemistry behind DEF helps clean up diesel exhaust.
Active Ingredient
Diesel exhaust fluid (DEF) primarily comprises two key ingredients – urea and deionized water. Urea, which makes up around 32.5% of DEF, is a compound formed from ammonia and carbon dioxide.
When injected into the selective catalytic reduction (SCR) system, the urea breaks down into ammonia, reacting with engine emissions to convert nitrogen oxides into harmless nitrogen gas and water vapor.
The remaining DEF is deionized water, making up around 67.5% of the fluid. Deionized water has had ions like calcium, chlorine, copper, magnesium, sodium, etc removed through an ion exchange process. This creates purified water that helps to prevent contaminants and minerals from interfering with the DEF and SCR system. The lack of minerals and contaminants allows the urea and deionized water to mix into a homogeneous solution.
So, in summary, DEF relies on two key ingredients – urea to provide the ammonia for reducing NOx emissions and deionized water to dilute the urea into an optimal solution. This combination is universal across all diesel vehicles and engines requiring DEF.
DEF Specifications
The International Organization for Standardization has set strict requirements for diesel exhaust fluid (DEF) (ISO). DEF’s necessary quality, composition, storage, and handling requirements are outlined in the ISO 22241 standard.
The ISO standard requires DEF to consist of high-purity urea dissolved with deionized water in a 32.5% urea solution. No other additives or chemicals are permitted. The urea must meet content, solubility, alkalinity, biuret, aldehydes, and insoluble matter specifications.
In terms of composition, DEF must have:
- Urea content between 31.8% and 33.2%
- Density between 1.0858 g/cm3 and 1.0934 g/cm3
- Refractive index between 1.3814 and 1.3843
- Alkalinity less than 0.2%
- Biuret less than 0.3%
- Aldehydes less than five ppm
- Insoluble matter less than 20 ppm
For storage and handling, the ISO standard requires DEF to remain stable and usable for at least one year after production if stored properly between -5°C and 30°C. DEF freezes around -11°C but can be used again after thawing with no degradation. Prolonged exposure to higher temperatures above 35°C can accelerate degradation. Materials like aluminum, copper, zinc, or uncoated steel are unsuitable for storing or handling DEF.
By meeting these precise ISO 22241 specifications, DEF products from all manufacturers are guaranteed to have consistent quality and compatibility for use in SCR emission control systems.
Universal Compatibility
All diesel exhaust fluid (DEF) meets the same ISO 22241 specifications and can be used interchangeably in any diesel vehicle that requires DEF.
The active ingredient in DEF is urea, which must be at least 32.5% purity for it to function properly. As long as the DEF meets the ISO specifications, the brand name does not matter.
DEF is required for diesel vehicles with selective catalytic reduction systems. SCR uses DEF to lower NOx emissions and meet EPA standards. Nitrogen and water vapor are produced when DEF is introduced into the exhaust stream because of a reaction between the urea and the NOx gases. The SCR system’s catalyst is where this reaction occurs.
The SCR system and catalyst are designed to work with any DEF brand that meets the ISO specifications. Vehicle manufacturers test their SCR systems using DEF from various manufacturers to ensure compatibility. So you can safely use DEF from any reputable brand for your diesel vehicle. The DEF brand does not impact performance or cause issues—only the purity level matters.
In summary, all major DEF brands are interchangeable and will work properly for any diesel vehicle that requires DEF. There is no need to use a special brand recommended by the vehicle manufacturer. Any DEF that meets the ISO 22241 standard will provide the same NOx-reducing results.
Quality Differences Between DEF Brands
While the active ingredient urea is chemically identical across DEF brands, slight variations in quality can result from manufacturers’ extra additives. However, all DEF brands certified by the American Petroleum Institute (API) must meet the same stringent specifications for purity and composition.
The key differences between DEF products lie in supplemental ingredients like:
- Stabilizers Help to prevent urea decomposition and maintain a longer shelf life. Some brands use more advanced stabilizer packages.
- Dyes are Added to help differentiate brands. Do not affect performance.
- Extra corrosion inhibitors may provide added protection for diesel engine components.
So, while major DEF brands use the same urea feedstock, some invest more in proprietary additive packages to enhance storage life and equipment protection. However, all certified DEFs still meet the required standards and can be considered interchangeable.
API certification is the key benchmark for ensuring quality. As long as DEF is API certified, fleet operators can be confident that it will perform identically to other brands when replenishing urea tanks.
Pricing
Regarding pricing, there are some differences between DEF brands and packaging options.
DEF is sold by the gallon, and it’s typically available in 1-gallon containers, 2.5-gallon jugs, 55-gallon drums, and 275-gallon totes. Bulk DEF in large containers is less expensive per gallon compared to the smaller packaged containers.
The pricing for bulk DEF in drums or totes can vary more between brands. Bulk pricing also depends on your geographic location and the distributor you purchase from. Some fleet operations or farms may get bulk DEF delivered, which helps lower the per-gallon cost. Bulk DEF can range from $2 – $3.50 per gallon.
When comparing DEF products, the bulk DEF options will be less expensive per gallon than packaged DEF. However, you need to factor in the upfront cost of a 55-gallon drum or 275-gallon tote and consider your actual DEF usage. For some diesel vehicle owners, a few 1-gallon jugs are more practical and cost-effective than buying bulk volumes of DEF.
Storage
Proper storage of diesel exhaust fluid (DEF) is important to maintain quality and effectiveness.
Here are some key storage considerations:
Shelf Life
- When stored properly, DEF has a limited shelf life of approximately 12 months. The urea content can degrade over time, reducing its effectiveness.
- Always check the expiration date on DEF containers before using them. Expired DEF should not be used and may cause issues.
Temperature Environment
- DEF freezes around 12°F (-11°C). It will thaw and return to liquid form once warmed, but repeated freeze/thaw cycles can affect quality.
- For best preservation, store DEF between 23-86°F (-5 – 30°C). Garage or indoor storage is ideal. If storing outdoors, avoid extreme cold.
Handling
- DEF is susceptible to contamination. Use clean funnels and containers. Do not transfer or store in used containers.
- Keep DEF containers sealed when not in use. Avoid spills. If left on surfaces, DEF can be corrosive to some materials.
- If DEF has been sitting for an extended time, agitate or stir it before dispensing. Sediment can settle, which needs to be re-mixed.
Properly stored DEF has a one-year shelf life. Keep it between 23-86°F, clean, and sealed. Follow the guidelines to maintain optimal quality and performance. Check expiration dates and avoid using degraded fluid.
FAQs
You asked, we answered:
Is All Diesel Exhaust Fluid the Same?
While the basic components of Diesel Exhaust Fluid (DEF) – water and urea – remain the same, different brands might have variable levels of purity and concentration. The standard for DEF is defined by ISO 22241, guaranteeing a specific concentration and purity of the urea solution.
What Changes Are Expected in DEF by 2024?
As of now, there are no announced changes to the standardized composition of Diesel Exhaust Fluid (DEF) in 2024. However, advancements towards more environmentally-friendly alternatives or enhancements might occur due to evolving regulations and global emission standards.
Are All Brands of DEF Compatible with My Vehicle?
As long as the Diesel Exhaust Fluid (DEF) meets the ISO 22241 standard, it should be compatible with any vehicle that requires DEF. However, it’s always best to check your vehicle’s user manual or consult your manufacturer.
Can I Create My Own DEF?
Creating your own DEF is not recommended due to the strict purity requirements. Impurities may cause severe damage to your vehicle’s Selective Catalytic Reduction (SCR) system.
Conclusion
Regarding diesel exhaust fluid (DEF), most major brands meet the same specifications and are universally compatible with diesel vehicles that require DEF. The active ingredient in DEF is urea, and all DEF must contain a 32.5% urea concentration to properly reduce diesel emissions.
The key factors in choosing a DEF brand are price, availability, storage considerations, and brand reputation. Most automotive parts stores carry multiple DEF brands, so purchasing comes down to personal preference.
Generally, the DEF brands are interchangeable and provide comparable performance. Testing has shown little difference between brands regarding DEF quality and effectiveness. Some brands may use slightly different stabilizers and inhibitors, but the urea concentration differs across brands.
When purchasing DEF, price and convenience are the driving factors for most consumers. Comparing prices and buying in bulk can offer cost savings over time. Properly storing DEF is also important, so purchasing DEF at locations where inventory moves quickly ensures freshness. Get in touch with Azure Chemical to receive top quality diesel exhaust fluid for your diesel truck.
