What is AdBlue?

If you’re the owner of a diesel car, chances are that you need to use AdBlue. But what is it, what does it do and what happens if we neglect to use it? Here, we clear everything up.

What is AdBlue and what does it do?

AdBlue is a diesel exhaust fluid (DEF) that helps diesel vehicles reduce the harmful emissions they create. It works alongside selective catalytic reduction systems to reduce the emission of nitrogen oxide from diesel engines.

What is AdBlue made of?

AdBlue is essentially a solution of deionised water (67.5%) and high-purity urea (32.5%), as set out in the ISO 22242 standard. It’s a colourless, non-toxic liquid that is stored in a separate tank and must be topped up occasionally by the driver.

What is AdBlue used for?

AdBlue is designed to help diesel vehicles meet the latest Euro 6 exhaust emission regulations by reducing the harmful emissions they create.

While diesel cars tend to emit less carbon emissions than petrol engines, they do produce more nitrogen oxide emissions which can negatively impact public health. Nitrogen oxide is a harmful gas that can affect the respiratory system, reducing lung function and increasing the risk of respiratory illnesses. It also contributes to air pollution.

For these reasons, many governments have set a limit on vehicular nitrogen oxide emissions and have promoted the use of AdBlue – which can effectively improve air quality and reduce the danger of pollution-related illnesses.

With environmental health now a top priority across the world, emission regulations have become increasingly stringent in recent years. Since September 2015, all new diesel cars have had to conform to the Euro 6 regulations, which cut the permissible limits for nitrogen oxide from 180mg/km to just 80mg/km.

These emissions are also a key measurement for deciding which cars can enter a Low Emission Zone, such as London’s Ultra Low Emission Zone, without paying a fee.

However, with the use of AdBlue, you can meet these emission standards and enter a low emission zone without being charged. In fact, according to TotalEnergies, AdBlue can reduce nitrogen oxide emissions by over 90% and hydrocarbon and carbon monoxide emissions by 50% to 90%, making it a crucial tool for improving air quality and combatting environmental issues.

How does it work?

AdBlue works alongside the selective catalytic reduction system in your diesel car. An injector automatically sprays small amounts of the AdBlue into the exhaust system.

Here, it mixes with the exhaust gases, and the ammonia within the urea reacts with the nitrogen oxide in the exhaust steam, converting the dangerous chemicals into nitrogen and water vapour. AdBlue is not a fuel additive as it’s added to the exhaust gas after combustion has taken place.

Does every diesel vehicle need AdBlue?

The Euro 6 emission standards came into action in September in 2015, so most diesel cars produced since then will use AdBlue. Not all of them do though, as there are other systems that can be used to reduce nitrogen oxide emissions such as exhaust gas recirculation (EGR).

Importantly though, AdBlue can only be used in a diesel vehicle that’s fitted with a selective catalytic reduction system. There will be some signs to show this – for example, the word ‘blue’ or letters ‘SCR’ may appear in the car’s name. Think Ford vehicles that are badged ‘EcoBlue’ or Volkswagen models which feature the letters ‘TDI SCR’. As mentioned above, you can also check if there’s an AdBlue filler where you usually find your fuel.

Notably, AdBlue’s effectiveness has long been proved, given that it has been commonly used in trucks and buses since 2006. This followed the introduction of the Euro 4 regulations which made it compulsory for all new lorries after 2006 to have a selective catalytic reduction system fitted on them.

With the transport industry being one of the biggest contributors to greenhouse gas emissions, the rules have only got stricter since then. In the most recent Euro 6 regulations, it’s stated that any truck producing more than 0.50 g/km of carbon monoxide and over 0.08 g/km of nitrogen must use AdBlue fluid.

How do I refill AdBlue?

You can refill AdBlue yourself, however, it’s important to remember that, while it’s non-toxic, it’s corrosive and can cause irritation to the skin, eyes and lungs. It’s therefore important to take some precautions – wear gloves and wash your hands after filling. And if it touches the vehicle’s paintwork, you should rinse the area with water.

We’d always recommend visiting your local Arnold Clark service centre, however, if you do no need to top up your AdBlue in an emergency, follow these steps:

1. Step 1

   Locate the AdBlue tank – this is usually next to the diesel filler cap, under the bonnet or in the boot, but check your manual if you’re unsure.

   

2. Step 2

   If you have one, attach an anti-spill nozzle to the AdBlue container. Otherwise, remove the tank cap and use a funnel.

   

3. Step 3

   Slowly refill the tank until it is full – your owner’s manual should tell you how much to use.

   

Alternatively, AdBlue pumps can be found at most big filling stations in the HGV lanes. Some of the pumps feature a specific fuelling nozzle for HGVs and a different one for cars.

If filling up AdBlue yourself, you should also note the following:

• Even though AdBlue looks like water, you shouldn’t refill your tank with ordinary tap water as you could damage your selective catalytic reduction system.
• It’s vital that you don’t pour your AdBlue into your diesel tank as this will cause a great deal of expensive damage to your fuel tank, pump and injection system. If this does happen, you should not start the vehicle and immediately call your breakdown company.

As mentioned before, your AdBlue will usually get topped up during a routine service. However, it’s important to know what to do if you do run out. Otherwise, most garages will do it for a small charge.

Your questions answered

Does my car need AdBlue?

If you drive a diesel car, it’s highly likely that you’ll need to use AdBlue. However, if you’re unsure, you can always check your vehicle handbook or check if you have a filler cap next to your fuel filler.

How much AdBlue will my car use?

This varies for different vehicles, but usage can be affected by driving style, journey type, engine and vehicle load and environmental conditions. Plus, the size of the AdBlue tank fitted to vehicle can vary between manufacturers and models, meaning the top-up intervals can differ.

For example, according to Ford, a tank of AdBlue can usually last between 2,330 miles and 6,835 miles following a refill, while Toyota claims this number to be around 9,000. According to Fleet Alliance though, “it is estimated that a passenger car will consume approximately 1.5 litres of AdBlue for every 620 miles.”

How do I know if my car needs more Adblue?

A warning light will come on in your car if you’re running low on AdBlue. This will appear long before the tank reaches empty – around 1,500 miles – but you should top it up as soon as possible. You can contact your local service centre or purchase some AdBlue and fill up the tank yourself. Some drivers can be fortunate enough not to require a fill-up between their annual services and MOTs.

What happens if I run out of AdBlue

If you run out of AdBlue while driving, your engine’s power and performance will be affected. The car will try and reduce the amount of emissions it’s producing by going into ‘limp mode’ – which effectively means its speed will reduce and the stereo or air conditioning may turn off.

You’ll find that many modern cars can’t be restarted if their AdBlue is empty. It’s always a good idea to keep a spare bottle to hand if this situation does occur. It's important to remember that, without AdBlue, diesel engines will produce more pollutants than is legally allowed, and they’ll fail any emission tests.

Is all AdBlue the same?

There are different names for AdBlue on the market, such as BlueDEF and BlueTEC, but all mixes will contain the solution of 32.5% of urea and 67,5% of de-ionised water. However, you can always trust the German Association of the Automotive Industry’s AdBlue marque, as it will definitely meet these requirements.

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

At Arnold Clark Autoparts, we have ten-litre bottles available. Most garages will top up your AdBlue for a small charge. You can also buy it from many fuel stations and numerous retailers with prices varying online.