Anti-Crystallization Additives for AdBlue®: Why and How to Use Them

AdBlue® (a mixture of 32.5% urea and demineralized water) is essential for reducing nitrogen oxide (NOx) emissions in modern diesel engines equipped with SCR (Selective Catalytic Reduction) systems.

However, AdBlue® is chemically unstable. Over time, or under certain conditions, it can degrade and form crystals (mostly cyanuric acid crystals). These deposits can clog the injector, block the lines, or damage sensors and catalysts, leading to costly repairs.

This is where anti-crystallization additives come in. They are designed either to prevent the formation of crystals or to dissolve them once they appear.

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Why Does AdBlue® Crystallize?

Several conditions increase the risk of crystallization in AdBlue®:

• Repeated short journeys: the SCR system does not reach its full working temperature, so AdBlue® doesn’t vaporize completely.
• Frequent stop-and-go driving: common in urban use (taxis, buses, delivery trucks).
• Vehicles used infrequently: when AdBlue® remains stagnant in the tank and pipes for long periods.
• Cold climates: low temperatures accelerate crystallization risks.
• Residual deposits: if AdBlue® dries around the injector nozzle, crystals form quickly.

These situations are common in both private vehicles and professional fleets.

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Main Categories of Additives

There are two fundamental approaches:

1.Stand-Alone Additives

Added manually to the AdBlue® tank alongside standard AdBlue®.

Examples include:

• Admax (Xenum)
• MécaTech D2U
• Tunap 987 / Tunap 988
• Warm Up
• Wynn’s Anti-Crystallization
• Bardahl Anti-Crystallization

These products are generally dosed at around 25–100 ml per 8–12 liters of AdBlue®, depending on the brand.

Functions:

• Prevent formation of cyanuric acid crystals.
• Dissolve existing crystals.
• Protect injectors, pumps, and sensors from clogging.
• Reduce the risk of SCR malfunction indicators appearing on the dashboard.

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2. Pre-Mixed Additized AdBlue®

Instead of adding a separate product, the AdBlue® itself already contains an anti-crystallization agent.

Main references:

• Total ClearNOx® (also known as Diaxol®)
• CleanR MAX® (Renault Trucks Oils)

Advantages:

• Ready to use (no need for manual dosing).
• Works for all vehicles equipped with SCR (cars, trucks, agricultural machinery, buses).
• More convenient for regular or professional use.

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3. International Additives (English References)

In addition to European products, other names often appear in the English-speaking market:

• 5in1 Blue+ AdBlue® Enhancer (250 ml)
• Wynn’s Crystal Clean & Protect (125 ml)
• Forté Exhaust Crystal Preventer (150 ml)

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Benefits of Using Anti-Crystallization Additives

• Maintenance savings: avoids injector or catalyst replacement.
• Cleaner system: prevents deposits in tanks, pipes, and dosing modules.
• Reliability: fewer dashboard warnings, limp modes, or engine power reductions.
• Universal use: suitable for cars, vans, trucks, and industrial diesel engines.
• Flexibility: can be preventive (regular use) or corrective (to clean an already affected system).

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Safety and Usage Recommendations

• Never pour into the diesel tank — additives are strictly for the AdBlue® reservoir.
• Use a funnel with a flexible spout to avoid splashing.
• Store in a dry place, away from sunlight, and keep tightly closed.
• Wear gloves and protective glasses — products may be irritating or flammable.
• Always respect the recommended dosage on the packaging.

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Conclusion

Crystallization is one of the main risks associated with AdBlue®. Left untreated, it can quickly cause SCR system failures, immobilize vehicles, and result in significant repair costs.

Using anti-crystallization additives — either as separate products or as part of pre-mixed AdBlue® solutions — is an effective way to:

• Protect the SCR system.
• Extend the service life of components.
• Guarantee cleaner emissions and lower operating costs.

For drivers making short trips, fleets operating in cities, or vehicles exposed to cold weather, these additives are a simple, preventive solution to a complex and expensive problem.