Sunday, March 7, 2021

Advantages and Disadvantages of Using AdBlue

What Is AdBlue?

AdBlue is a colourless, slippery, non-flammable liquid made up of 32.5% urea and 67.5% deionised water. It is not toxic and it is not a fuel additive — it never mixes with the engine or the fuel tank.

It is used in SCR (Selective Catalytic Reduction) systems, the most effective method available for reducing nitrogen oxide (NOx) emissions. NOx is a toxic gas formed when fuel burns with air, and it directly affects human respiratory health.

How Does the SCR System Work?

SCR is an exhaust aftertreatment system. As combustion takes place, AdBlue is injected into the SCR catalyst, where it reacts with the exhaust gas and converts harmful NOx into harmless nitrogen and water vapour.

The fluid is held in its own tank, completely separate from the diesel tank, and metered into the exhaust line by a dedicated pump and injector.

The results:

Up to 85% reduction in NOx emissions
Around 40% reduction in harmful exhaust particulates
Compliance with Euro 4, Euro 5 and Euro 6 standards, accepted across all EU countries
Lower fuel consumption at those emission standards

Consumption: AdBlue is used at a rate of 2% to 6% of diesel consumed, depending on load and operating conditions. It is available at most fuel stations.

Why Mostly Trucks and Construction Machinery?

SCR is widespread on trucks, tractor units and construction machinery, but less common on passenger cars. There are three reasons:

The system is expensive.
The AdBlue tank takes up significant space, which is hard to find in a passenger car.
Passenger cars run at lower engine load and therefore lower exhaust temperature, and already produce less NOx.

Once fitted, an SCR system lasts the life of the vehicle. It does not affect oil change intervals.

Advantages of Using AdBlue

Advantage	Detail
Substantially reduces air pollution	Cuts NOx emissions from heavy and commercial vehicles, indirectly helping prevent respiratory illness
Non-flammable	Safe to store and transport
Usable again after freezing	Begins to freeze at −11 °C; once thawed it works normally
Reduces solid waste	Particulate emissions fall alongside NOx
Regulatory compliance	Meets Euro 4/5/6 requirements across the EU

Disadvantages of Using AdBlue

Disadvantage	Detail
Requires a separate tank	Takes up additional space on the vehicle
The vehicle cannot move if it runs out	Emissions rise, the engine derates and eventually will not run; recovery costs both time and money
Running dry damages the catalyst	An SCR system operated without fluid can suffer catalyst damage
Freezes at −11 °C	Below that the system must be heated, otherwise the vehicle will not run
Corrosive over time	Causes corrosion particularly on copper components, and deposit build-up in the SCR system; filters need regular checks

What This Means for the Workshop

Most AdBlue faults come from a limited set of causes: crystallised deposits at the injector, a failed pump, contaminated or out-of-specification fluid, a faulty NOx or level sensor, and neglected filters. Because a fault here derates the vehicle, diagnostic speed has a direct commercial consequence — a truck stopped by AdBlue is a truck earning nothing.

Reading SCR faults correctly requires a tool with heavy vehicle coverage that can show live data for NOx sensors and dosing rate, and run system tests. Nitro Bilişim supplies this equipment and tests it on real vehicles at our Adana application centre.