AdBlue: Problems, DPFS, between myth and reality + Tips!

AdBlue is a solution composed of 67.5% demineralised water and 32.5% urea. Its main use is to reduce nitrogen oxide (NOx) emissions from diesel engines, in response to strict environmental standards such asEuro 6. By converting NOx into nitrogen and water vapour, AdBlue plays a role in protecting the environment.

Before going any further on the subject, it's important for us to explain what the famous SCR system is.

The SCR (Selective Catalytic Reduction) system is a pollution control technology used on diesel vehicles to reduce emissions of nitrogen oxides, which are responsible for atmospheric pollution. It works by injecting AdBlue directly into the exhaust gases before they pass through a special catalyst. Under the effect of heat, AdBlue breaks down into ammonia, which then reacts with NOx to transform it into nitrogen and water vapour (H₂O), elements that are harmless to the environment.

The problems associated with AdBlue

Despite its environmental benefits, this colourless liquid sometimes causes annoying technical problems for motorists, and it's divisive to say the least. Common problems include crystallisation of AdBlue when exposed to temperatures that are either too low or too high, causing clogging of injectors and the SCR system.

Another common problem is malfunctioning of the AdBlue level or quality sensor, leading to stressful error messages for the driver, or even an inability to start the vehicle.

To ensure that you are using quality AdBlue, it is essential to check that it complies with the ISO 22241 standard, which sets out rigorous criteria for its composition, manufacture and storage. This standard is broken down into several "sub-standards":

AdBlue standard ISO 22241-1

This standard governs product quality requirements.

AdBlue standard ISO 22241-2

It defines the test methods for guaranteeing its purity.

AdBlue standard ISO 22241-3

Sets out good handling, transport and storage practices to avoid contamination.

AdBlue standard ISO 22241-4

Controls the filling interface, guaranteeing perfect compatibility with vehicle tanks.

Any product bearing the AdBlue® mark must therefore meet these requirements, ensuring optimum operation of the SCR system and avoiding the risk of crystallisation or clogging.

Other points to bear in mind. A good AdBlue must be colourless and odourless; any suspicious colouring or smell may indicate contamination.

The use of an anti-crystalliser for AdBlue can be an interesting solution for preventing one of the most common problems associated with this product: crystallisation.

This 'additive for additives' is designed to keep AdBlue in a liquid state, thereby limiting the formation of solid deposits that can clog the SCR system and its injectors. Anti-crystallisers work by lowering the temperature at which AdBlue begins to crystallise, protecting the system even during severe weather variations or extreme winter temperatures. However, before using an anti-crystalliser, it is important to check that it is compatible with your vehicle, and to choose recognised brands to avoid introducing other malfunctions or a loss of efficiency in your anti-pollution system.

Modern anti-pollution systems, such as the particulate filter (DPF) and the SCR system, play a key role in reducing pollutant emissions from diesel vehicles. However, over time, these systems can become clogged and require specific maintenance to remain effective and comply with environmental standards.

Regeneration: essential automatic cleaning

The particulate filter (DPF) is designed to capture the fine particles produced by diesel combustion. To prevent it from clogging up, it undergoes automatic regeneration, a process in which the deposits are burnt off at high temperature during certain driving cycles (motorway or heavy acceleration). A vehicle used mainly in town, with short journeys, does not always trigger this regeneration, which can lead to the clogging of the DPFS and the lighting up of a warning light on the dashboard.

Repair and replacement of anti-pollution systems

If regeneration is no longer sufficient, or if the DPF/SCR is too clogged, it can be cleaned manually by a professional using a chemical treatment or a special machine. In some cases, it may be necessary to replace the particulate filter or SCR catalytic converter to ensure that the engine runs smoothly and complies with pollutant emission standards.

Removing a DPF or SCR system: an illegal practice

Faced with the cost of repair or replacement, some motorists are tempted to remove their particulate filter or deactivate their SCR system to avoid maintenance worries. However, this practice is strictly forbidden by law, and not only carries penalties (fines, immobilisation of the vehicle), but also systematically fails the roadworthiness test. What's more, driving without this equipment considerably increases pollutant emissions and can lead to engine malfunction in the long term.

under article L.318-3 of the Highway Code, it is strictly forbidden to remove a pollution control device, such as a particulate filter (DPF). Any modification aimed at eliminating or altering the effectiveness of these systems may result in a fine of up to €7,500. This ban does not apply to older vehicles that were not fitted with such systems at the time of manufacture.

To round off this FAQ in style, we've put together a compilation of 4 myths about AdBlue that we've heard from our customers since 2008. Some of them, as you'll see, are pretty funny.

Myth 1: You can drive indefinitely without AdBlue

This is not true. Vehicles fitted with an SCR system cannot run without AdBlue. A lack of AdBlue can bring the vehicle to a standstill, as the system is designed to prevent it from operating in the event of running out of fuel.

Myth 2: AdBlue can be replaced by water or other substances

A dangerously mistaken idea. AdBlue is a specific solution that cannot be substituted without risking serious damage to the emission reduction system.

Myth 3: Deactivating AdBlue has no impact on the vehicle

It is possible to deactivate the AdBlue, but be careful, as this will mean that your vehicle no longer complies with the current anti-pollution standards. Make sure you take this into account.

Myth 4: Urine can be used as a substitute for AdBlue

There's a crazy myth that urea-rich urine can replace AdBlue in diesel SCR systems. However, this idea is completely false. Although urea is a key component of AdBlue, the commercial solution contains a concentration and purity that are specifically controlled so as not to damage the components of the emission reduction system.

Using urine, which contains many other compounds and impurities, could cause irreversible damage to the system and reduce the effectiveness of NOx reduction, compromising vehicle performance and compliance with environmental standards.