The technical guide to AdBlue

By: Bill Savidan

MCD gives the low-down on what’s new and interesting in the world of RV technology. This month, we're talking AdBlue

While the local transport industry has been coming to grips with the introduction of AdBlue®*, it has quietly slipped under the radar of most diesel-powered motorhome owners. But AdBlue is here now, and it is here to stay.

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So, what is AdBlue and why do we have it? AdBlue is a colourless, synthetically produced, 32.5 percent solution of pure urea in demineralised water.

It’s introduced into the exhaust gases of a diesel motor to reduce the nitrous oxide present to acceptable levels. But what are acceptable levels?

Historical context

It started in Europe. The European Union ‘Euro 1’ diesel engine emissions legislation was introduced in 1993 with the aim to reduce pollution caused by the exhaust gases from diesel-powered vehicle engines.

EU diesel emission standards have been progressively upgraded since then. The programme has been effective so far, reducing nitrous oxide by more than 75 percent and particulate matter by 95 percent. In September this year, the latest standard—Euro 6—becomes effective in the EU.

Methods used to meet EU emission standards

The methods most commonly employed are Diesel Particulate Filters (DPF), Exhaust Gas Recirculation (EGR), and Selective Catalytic Reduction (SCR). For example, motors around 2.5 litres or less in size complied with current Euro 5 requirements by being factory-fitted with a DPF and/or an EGR system.

These systems proved ineffective cleaning the exhaust gases from larger diesel motors so their manufacturers opted for the more effective SCR system using AdBlue. 

The new Euro 6 emission standards being introduced in September are tough to meet. In most cases, motors 2.5 litres or less in capacity fitted with DPF and EGR systems individually or combined failed to meet Euro 6 standards. As a result, from September, most European diesel motor manufacturers will add an SCR system using AdBlue to meet this higher emission standard.

Who will it affect?

In the next few months, as stocks of Euro 5 diesel-powered motorhomes run out, new stock built on the popular brands—Ford, VW, Mercedes-Benz, Fiat, Iveco, Renault, and Citroen—will be fitted with SCR systems dispensing AdBlue into the vehicle’s exhaust gases.

The only people directly affected will be those who purchase a vehicle fitted with an AdBlue system.

How will it affect them?

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They will have to refill the AdBlue tank when it runs out. The most visible sign that an AdBlue SCR system is fitted to a vehicle is the blue (for AdBlue) cap on a separate filler pipe located next to the black cap on the diesel filler pipe. The tank holds enough AdBlue for around 10,000 to 14,000km of travel.

Warning messages come up on the dashboard display when an AdBlue top-up is required. If the AdBlue tank empties, safeguards include restricting the motor to 60 percent of its normal power output until the AdBlue tank is refilled, and/or not allowing the motor to start until the tank is refilled.

AdBlue is available for purchase now at some service stations and at some vehicle franchise parts departments. Mercedes-Benz and Ford dealerships have bulk supplies in their workshops to top up AdBlue tanks as part of the vehicles regular service programme.

BNT Automotive, a nationwide retailer, has AdBlue in stock in 10-litre packs.


Contamination of AdBlue is an issue. Most AdBlue containers are fitted with a dispensing nozzle to ensure the transfer from bottle to tank is clean.

But by far, the most common cause of contamination is caused by an operator error when AdBlue is put directly into the diesel tank or diesel is pumped into the AdBlue tank.

It costs time and money to rectify the problem if discovered on the forecourt. It can cost a lot more if the vehicle is driven off before the error is discovered.

Why do we need to have vehicles fitted with AdBlue systems when New Zealand emission standards don’t require it?

We have no choice. All new European diesel-powered vehicles will have the SCR systems factory fitted and vehicle computer systems that have programmed safeguards built in that reduce the vehicle’s performance if the SCR system is interfered with.

How do these emission requirements affect diesel-powered vehicles in New Zealand?

Three years ago, New Zealand informally adopted the European exhaust emission regime to the extent that diesel-powered vehicles newly registered in New Zealand had to comply with the Euro 4 emission standard.

Sometime in the future, this standard will be upgraded to Euro 5 and then Euro 6. All diesel-powered vehicles currently registered can still be used on New Zealand roads.

*AdBlue® is a registered trademark of the Verband der Automobilindustrie e. V. (VDA). Thanks to Rod Simmonds from Chemsafe Manufacturing Ltd, Pukekohe, for the background material he provided.

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