What is AdBlue, how is it refilled and why do diesel cars use it?

A practical guide for drivers


GOVERNMENTS and the car industry are working towards increasingly stringent emissions regulations. They are put in place by the EU to protect air quality and the health of the population.

With technology such as turbocharging, manufacturers are making their engines ever more efficient, but sometimes a more radical idea is needed. The Euro 6 regulations that came in last year have forced the makers of diesel cars in particular to find new ways to reduce harmful emissions.


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What is AdBlue?

One of the latest techniques used to clean up diesel emissions is known as selective catalytic reduction (SCR). A solution of urea in water is used to treat exhaust gases and remove harmful pollutants, including nitrogen oxides (NOx), of which nitrogen dioxide (NO2) is the most harmful.

The fluid used in most vehicles is known as AdBlue, a registered trademark owned by the German Association of the Automobile Industry (VDA), which ensures standards are maintained. The fluid is stored in a tank in the car, but unlike petrol or diesel it is not injected into the engine; instead it is fed into part of the vehicle’s exhaust. A chemical reaction converts the harmful NOx exhaust gases into harmless nitrogen and water.

What cars use AdBlue?

New technology such as SCR and AdBlue is still found mainly in large, expensive diesel models. That is because the system is both too large and too expensive to squeeze into small runabouts.

In tests, small diesel cars without SCR, such as the 2016 Volkswagen Polo 1.4 TDI, have been found to be as toxic as a fully laden lorry. In measurements taken by Leeds University’s Institute of Transport Studies, the Polo emitted 1.2g of NO2 per kilometre travelled, which is the same as a fully laden diesel lorry with a 13-litre engine.

How do I know if my car uses AdBlue?

When you buy a new or used diesel car from a dealership, the sales person should explain what features it has and specifically whether it uses AdBlue. Some cars have a blue or black screw cap for AdBlue next to the black diesel filler cap. In others, the cap is in the boot, or in the engine compartment. The vehicle handbook will explain the requirements of your car’s system.

How often do you need to refill the AdBlue?

The tank that holds the AdBlue solution varies in size between makes and models of car. As a guide, a Volkswagen Tiguan SUV and Passat family car have a 12 and 13-litre AdBlue tank respectively.

The rate it is consumed depends on the driving style; the more economical drivers are, the slower it will be used up. VW estimates that the Tiguan and Passat use 1.5 litres of AdBlue every 620 miles, and suggests that a tankful of AdBlue gives a driving range of 3,000-4,000 miles for the Tiguan, and 4,000-6,500 miles for the Passat.

By contrast, Peugeot estimates that its cars can travel 12,000 miles between refills — the same as its servicing intervals.

How will drivers know if AdBlue needs topping up?

The car’s driver information display screen should flash up warnings, much as it would if fuel or windscreen washer fluid were low.

Failing to act on these warnings will ultimately result in the car refusing to start until the AdBlue tank is filled.

Can drivers refill it themselves, and how much does it cost?

Garages should refill AdBlue as part of a diesel car’s routine servicing. However, it’s possible to refill a tank of AdBlue yourself.

Some service stations have AdBlue dispensing pumps. Alternatively, garages and filling stations sell portable containers of AdBlue, as do many online retailers, such as Amazon.co.uk (click here) and Halfords.com (click here). Prices start at roughly £5 for a 4.7-litre container.

Some car makers, including Peugeot, suggest you take the car to a dealer, which will do a refill for a fixed price of £9.99. Vauxhall offers to waive any labour charge if drivers bring their car in for a top-up.

Emergency top-up bottles of AdBlue

Some high-mileage drivers carry 1-litre emergency bottles of AdBlue in the boot of their car, safe in the knowledge that should they need to fill the system at short notice, they will be able to do so. The fluid is corrosive, so some car companies do not recommend this.

AdBlue and your car’s warranty

If your car has a warranty, it is important to use branded AdBlue solution. For any solution to use this trademark, it must comply with certain standards that vehicle manufacturers’ SCR systems rely on. Failing to do so could invalidate the warranty.

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