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What is AdBlue?

Ever wonder what Adblue is? If you want to buy a new or used diesel engine car, you will probably have heard the word "AdBlue" mentioned before more than a few times. It was first launched by Tetrosyl under the Carlube brand back in 2009. AdBlue, also known as DEF (Diesel Exhaust Fluid) or AUS 32, is essential in the operation of diesel particulate filters (DPF) with SCR (Selective Catalytic Reduction) technology.


AdBlue is the brand name used for a type of fluid designed for the catalytic convertor connected to some diesel car exhaust systems.

Everything you need to know about AdBlue

So, now you know what AdBlue is. With the evolution of anti-pollution standards, car manufacturers must constantly offer new alternatives to reduce greenhouse gas emissions. As a result, more and more of these cars are now equipped with SCR devices in an attempt to reduce diesel vehicles' impact on the environment. It is a liquid solution that eliminates a large part of the nitrogen oxides resulting from diesel combustion.


The composition of AdBlue

AdBlue is a liquid solution specially designed for vehicles running on diesel. Composed of 32.5% urea solution and 67.5% demineralised water, AdBlue allows the nitrogen oxides emitted by running diesel engines to be changed into water vapour and nitrogen, making the component harmless for people and the environment. This component is found only in vehicles with SCR technology (Selective Catalytic Reduction).


AdBlue is colourless, biodegradable, non-toxic, non-explosive, non-flammable and does not present any major danger to health or the environment. The use of AdBlue is essential in the operation of SCR technology particulate filters and reduces nitrogen oxide (NOx) emissions by 80% to 90%. Because if the FAP manages to capture most of the particles, it cannot, however, capture the nitrogen oxides (NOx) because these are too small. SCR devices using AdBlue are becoming more and more democratised. Since 2006, it's been compulsory for all heavy goods vehicles that run on diesel. Most car manufacturers now offer at least one vehicle incorporating a fuel tank.


How does AdBlue work?


When a diesel vehicle is driving, the system sends AdBlue upstream of the SCR device. Under the effect of the heat coming from the exhaust fumes, the urea solution that makes up AdBlue changes into carbon dioxide and ammonia. Passing through the SCR catalyst, the ammonia resulting from the transformation of AdBlue will undergo a chemical reaction when it comes into contact with the nitrogen oxides released following the combustion process. Only water vapour (H20) and nitrogen (N2) will remain at the outlet of the catalyst.


What is the AdBlue warning light that comes on the dashboard?

As with other liquid compounds found in vehicles, you should regularly monitor the AdBlue level. For this reason, cars running on AdBlue all have a specially designed warning light on their dashboard to alert the driver that the AdBlue tank will soon run dry. This warning light can either be in the form of a blue fuel pump with the wording "AdBlue" or the words "CHECK UREA SYSTEM" or a fuel pump changing from black to orange and then to red.


There's no need to panic when this light comes on. Even if it tells the user that the AdBlue tank will soon be empty, they will still have an average of 2,400 km before they really run out of fuel. Nevertheless, it will not be necessary to wait too long before refilling AdBlue because vehicles whose AdBlue reserves are completely empty will generally refuse to start until the user has added at least 5 litres to the tank.


Where can I fill up my diesel vehicle with AdBlue?

Like all fluids that keep a car running correctly, you must occasionally top up the AdBlue tank. In normal driving, vehicles consume one litre of AdBlue for every 1,000 kilometres. Vehicles are usually equipped with tanks of around twenty litres, which can drive for 20,000 kilometres before having to refill AdBlue.


To fill your AdBlue tank, you must first locate the characteristic light-blue cap. While it is usually found under the fuel filler flap next to the diesel cap in newer vehicles, the caps are more likely to be found in the boot or near the engine block in older cars. Once the cap has been identified, all you have to do is fill the tank enough to be able to leave without risk. Checking your vehicle's handbook for instructions is always a good idea.


How to fill the AdBlue tank?

Canisters are suitable for topping up, although sometimes a funnel is provided. If the tank is almost empty, it must be filled with at least 4 litres. Do not fill it to the brim or fill it up before the light comes on. If the filling of AdBlue exceeds the tank's maximum capacity, the liquid can go up in the pipe, which risks crystallising and blocking the vent. This will degrade the tank, which will then need to be replaced. It is quite possible to ask to have this operation carried out in a workshop of the vehicle brand or, to save costs, in a garage or an approved service workshop.

Another precaution, especially if the hole is under the fuel filler flap, is to never pour diesel into the blue hole and never pour AdBlue into the fuel tank. Dispose of any AdBlue left in the container, as it will degrade over time. Please note that AdBlue is not a diesel additive, so it should never be mixed directly with fuel.

Frequently asked questions about AdBlue

What should I do if my Adblue tank is empty?

Please take care to avoid having an empty AdBlue tank. Being approved to operate with their particulate filters, cars using AdBlue must never run dry. The system will switch the engine to degraded mode to prevent the vehicle from driving without AdBlue by limiting the speed (in the best case), imposing a complete stoppage of the engine or preventing the vehicle from restarting before refuelling (at least 5L). However, don't panic. You will be alerted well in advance by a message when your car starts, telling you the number of kilometres or miles remaining before the system goes into the degraded mode or locks up. These messages begin to appear when only a 2,400 km range of AdBlue remains.


Where can I buy AdBlue?

Many places sell AdBlue, including auto parts stores and petrol stations. You can also order it online and send it to your home or business. The most common method is to buy a canister of AdBlue. AdBlue cans for cars are packaged in 5L or 10L cans. Professionals can buy 210L or even 1,000L tanks, ideal for a fleet of trucks. However, keep in mind that AdBlue can be stored, under ideal conditions, for up to 18 months from the date of production. Some fuel stations offer pumps dedicated to AdBlue. They are still a minority, but their number is growing.

What should I do if I put AdBlue in the wrong tank

If you accidentally put AdBlue in the diesel tank, you must call a mechanic because there is a very high risk of damaging your car's engine. It can lead to costly repairs in terms of labour and the cost of replacing parts.

What should I do if I put diesel in the AdBlue tank?

You should be aware that a single drop of diesel in the AdBlue tank can contaminate several litres of AdBlue or even a full tank. If you ever put diesel in the AdBlue tank, do not start your car; you will dangerously damage the car's SCR system, which will cause the vehicle to be immobilised and incur high replacement costs. Quickly contact a mechanic or your dealership.


Is AdBlue considered to be dangerous?

AdBlue is non-toxic, non-flammable and does not explode. Simply rinse your hands with water after coming into contact with AdBlue. It can leave whitish or greyish marks on bodywork and clothing, but any stains can be easily rinsed away with water. AdBlue spilt can make the ground slippery, but all it takes to remove any hazard is a quick hose down with water.


What precautions to take when using Adblue in freezing weather?

AdBlue crystallises at -11° C. A car parked under this temperature does not require any particular anticipation. The standards require manufacturers to have an automatic heating system to make the solution liquid activate the SCR within 20 minutes after start-up.


What about AdBlue when storing a car?

AdBlue has a shelf life of over a year. But if the car has been stored for many months or has travelled very few kilometres over a year, it may be advisable to have the tank drained to renew the product.

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