What is AdBlue and why do you need it?

What is AdBlue and why do you need it?
AdBlue is becoming increasingly common in new diesel cars as carmakers seek to meet increasingly stringent environmental regulations.

But what is AdBlue, how does it reduce nitrogen-oxide emissions and what happens if you neglect to use it? Read on to find out more.

What is AdBlue and why do we need it?

AdBlue is a non-toxic, non-flammable, odourless and biodegradable solution designed to help diesel vehicles meet the latest Euro 6 exhaust emission regulations.

It works in conjunction with a treatment system known as Selective Catalytic Reduction (SCR) and is used by an increasing number of carmakers.

What is AdBlue made from?

What is AdBlue

AdBlue is made from a urea and water solution, which is stored in a separate tank.

READ MORE: Should you buy a petrol or a diesel?

How does AdBlue work?

It is injected into a modified section of the vehicle’s exhaust, where it creates a chemical reaction, removing the harmful nitrogen-oxide emissions (NOx) and converting them into harmless water and nitrogen.

What happens if I don’t use AdBlue?

If a SCR-equipped vehicle runs out of AdBlue, it will fail to start. But don’t worry, because a warning message will appear on the dashboard, alerting you that the level of AdBlue is running low.

In the case of Volkswagen, the first message appears when the remaining range is 1,500 miles, and is repeated every 62 miles until the range reaches 1,000 miles. At this point the message turns amber and is repeated every 31 miles.

Eventually, the warning turns red, before the car will not restart and the ignition is turned off.

Does every diesel need AdBlue?

AdBlue should only be used in diesel cars fitted with an SCR system, so if in doubt, consult the vehicle handbook. As a rule of thumb, the more recently the diesel car was built, the more likely it is to use AdBlue, as the Euro 6 regulations were introduced in 2014.

FIND OUT: Your car's Euro emissions rating here

For example, SCR technology is fitted to all Land Rover diesel vehicles built from the 2016 model-year, while Jaguar, Audi, Citroen, Peugeot, Mercedes-Benz, SEAT, Skoda and Volkswagen all use AdBlue tech.

How do I refill my AdBlue?

Firstly, consult the handbook to locate the tank filler location along with any special instructions. Typically, the AdBlue filler will be found next to the fuel filler nozzle, but other locations include the spare wheel well or either side of the boot.


Open the filler cap, usually by hand, although some vehicles require the use of a wheel brace in order to release the cap. Screw on the connector of the refill bottle and allow the AdBlue to drain into the tank. Some systems require a minimum amount, so consult the handbook.

Peugeot recommends that, due to the position of the tank, the refill is carried out by a local dealer, but says that if you intend to do it yourself, the vehicle must be on a flat surface with the engine switched off.

Be aware that although AdBlue is non-toxic, it is corrosive and can cause irritation to the skin, eyes and lungs. Wear gloves and wash your hands and arms after filling. If AdBlue comes into contact with the vehicle’s paintwork, rinse the area with water.

MORE ADVICE: What is a hybrid car and should I buy one?

How much AdBlue will my car use?

How much AdBlue you use is determined by a number of factors, including journey type, driving style, environmental conditions and mileage. Some drivers might be fortunate enough not to require fill-ups between annual services.


A passenger car might consume 1.5 litres of AdBlue every 620 miles, with the size of tank determined by the size of car. For example, the Volkswagen Touran features an 11-litre tank, while the larger Touareg boasts a 19.5-litre tank.

Volkswagen says you can expect the first AdBlue warning message to appear at 3,000 to 4,000 miles in a Touran or 6,000 to 7,000 miles in a Touareg. Peugeot is more optimistic, claiming the AdBlue will need to be topped up every 12,500 miles.

How much does AdBlue cost and where can I buy it?

A 10-litre bottle of AdBlue should cost around £10 from a motoring discount store, while a main dealer might charge £1.50 per litre. Peugeot offers 10 litres of AdBlue for a fixed price of £9.99.

It’s worth noting that AdBlue degrades over time, so there’s little point keeping unused solution in the garage.

READ NEXT: Engine idling contributing to 40,000 deaths - what's being done?