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

A practical guide for drivers


GOVERNMENTS and the car industry have been working towards cleaner, greener cars for decades, with technology such as turbocharging to make engines ever more efficient. But sometimes a more radical idea is needed, and with the focus on toxic gases from diesel cars in particular focus in recent years, new ways to reduce harmful emissions have been needed. AdBlue is a great way to make diesel vehicle much less harmful to our health.

What is AdBlue?

One of the latest techniques used to clean up diesel emissions is known as selective catalytic reduction (SCR). A liquid 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 is AdBlue made of?

Some believe that AdBlue is made from pig urine and is blue in colour, but neither is true. AdBlue is actually a colourless liquid made up of high purity urea and deionized water.

Which cars use AdBlue?

New technology such as SCR and AdBlue is still found mainly in big, 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.

Does my car use 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.

Wherever the filler is, your car will warn you on the dashboard if the AdBlue tank needs a top up (see below).

How long does AdBlue last?

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 at which it is consumed depends on the size of the car and the driving style; the more economical the car and driver, the slower it will be used. 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 AdBlue themselves?

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 and Halfords.com.

Where to buy AdBlue

As we mentioned above, some service stations will have AdBlue dispensers which you can use to refill your tank. Other places you can buy AdBlue from include:

How much is AdBlue?

The price of AdBlue starts at roughly £5 for a 4.7-litre container, at the time of writing.

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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