What to do with AdBlue

AdBlue tips

Should you own, or lease, a modern Euro 6 (VI) diesel car, you may have to consider that it needs another fluid.

Diesel Emission Fluid (known also by its tradename, AdBlue) is harmless, made from mainly pure water and urea. Yet, it causes serious damage to the car, if dosed incorrectly.

What is the AdBlue system?

AdBlue fluid is a vital part of the car's Selective Catalytic Reduction (SCR) technology. The fluid is not injected into the engine but the exhaust system. This is performed automatically to reduce harmful NOx exhaust gases from polluting the air. Many cars will display an amber warning light on their fascias, should there be an issue, the meaning of which must be heeded, by consulting the owner's manual. These include top-up reminders.

How does the AdBlue system work?

When AdBlue is injected into the hot exhaust system, the heat present causes it to evaporate, leaving ammonia and carbon dioxide behind. As the exhaust gases flow into a catalytic converter within the exhaust system, the damaging NOx content reacts with the ammonia to form innocuous nitrogen and water.

How much AdBlue should I add?

Most drivers dose additional AdBlue, when warned by the dashboard message. Typically, this gives plenty of warning with a mileage countdown. Some garages do so at service time, anyway.

When considering AdBlue consumption, driving technique plays a big part. The harder you drive, the more AdBlue is used. Typically, expect 1.0-litre to be consumed every 600 miles.

What goes wrong with AdBlue systems?

For this article, we shall consider issues that are caused by driver error, rather than those arising from wear and tear.

If you allow the AdBlue tank to run empty, the engine is unlikely to restart, even after you have refilled the tank. It may not be possible to reset the AdBlue warning afterwards without professional diagnostic equipment.

You will cause serious damage, by dosing AdBlue in the wrong place. Never add it to the fuel tank, cooling system, or oil sump. Be familiar with the AdBlue tank's location. Spillages are avoidable, by using a suitable bottle.

Never overfill the system, either. This situation can create a vacuum within the tank that prevents the AdBlue from being injected into the exhaust. Consequentially, the AdBlue light may remain illuminated after filling. The AdBlue pump and circuitry are located on top of the tank in some cars. Overfilling, therefore, risks moisture contamination that can damage the electrical system.

AdBlue expiry

The AdBlue system cannot work correctly with out-of-date fluid, which has a finite shelf life. Never use AdBlue after the bottle's expiry date has passed and, unless you cover very high mileages, do not stockpile large quantities at home.

Ultra-violet light speeds up AdBlue’s deterioration and this can damage your exhaust system’s delicate Selective Catalytic Reduction catalyst. Therefore, buying bottles that have been sitting outside a petrol forecourt may not be a good idea. Instead, look for bottles that have been stored indoors, or in the dark.

Can I switch the AdBlue system off?

While some garages advertise AdBlue removal services, we advise against it. Anti-social implications aside, it results in you breaking the law. The UK government has useful information on this issue, should you be considering it: https://www.gov.uk/government/publications/modifying-your-vehicles-emissions/modifying-your-vehicles-emissions-the-legal-safety-and-health-implications

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