July 29, 2016

As global concerns for environment deepen, the motoring industry is taking more steps to ensure that new cars are producing cleaner emissions. For diesel vehicles, the introduction of AdBlue has been commonplace, with many manufacturers equipping their newer models with systems that use the fluid to produce less harmful emissions. 

If you have recently bought new diesel vehicles for your fleet, you may well have noticed the presence of a smaller blue or black cap adjacent to the main fuel cap — this is for AdBlue. This product is set to play a big part in the greener future of the industry, so it is important that you know what it is and what you need to do with it.

To dispel any confusion and to make sure you are reliably informed about this essential product, we’ve put together this comprehensive guide that contains everything you need to know about AdBlue. Read on to find out more.

AdBlue filling point in car

© Kickaffe - licence

What is AdBlue?

AdBlue is a colourless liquid that is made from a mixture of high-purity urea (32.5%) and deionized water (67.5%). The solution is an essential component of selective catalytic reduction (SCR) technology, which is one of the most effective systems for reducing the nitrogen oxide (NOx) levels in the exhaust fumes that are outputted by diesel engines. NOx is one of the most harmful pollutants emitted by engines, as it reacts with other gases in the atmosphere to form small particles and ozone, both of which can damage sensitive lung tissue in humans and animals.

When the fuel is burned by the engine, AdBlue is injected into the SCR catalyst in order to convert the NOx into a less harmful mixture of nitrogen and water vapour. The solution is stored in its own tank, separate from the diesel, before being added to outgoing exhaust gas by a dosing control system that supplies enough AdBlue to make up 2–6% of the total fuel consumption. In the SCR catalytic converter, the urea present becomes ammonia when heated, reacting with the NOx in the emissions to convert the pollutants into nitrogen, water, and a small amount of carbon dioxide —elements that are already natural to the air that we breathe.

Is AdBlue a fuel or fuel additive?

AdBlue is not a fuel itself or a fuel additive: it has its own tank and is stored completely separately to your vehicle’s fuel. It works as part of a selective catalytic reduction system (SCR), which you can see in the diagram below:

AdBlue system in diesel engines - selective catalytic reduction system (SCR)

© Rix Petroleum

Why is AdBlue so important?

As AdBlue is one of the most efficient ways of keeping the NOx levels in fuel emissions to a minimum, it has an incredibly important role to play in the future of diesel vehicles. SCR technology was first prescribed for diesel truck engines that had to meet the requirements of the fuel legislation, which was introduced by the European Union (EU) through a series of directives. These directives aim to define acceptable levels for exhaust emissions in new vehicles produced within the EU and European Economic Area (EEA) member states.

Car exhausts

The newest EU standard for cars and light commercial vehicles is Euro 6, which was introduced for new type approvals in September 2014 and for all new cars in September 2015. Heavy-duty vehicles like trucks and buses have their own standards, with the latest being Euro VI, first enacted in December 2013. Both of these regulations have even more ambitious targets for keeping exhaust emission levels low in both petrol and diesel vehicles.

Within the dual standards system, there are categories for different sizes, where larger vehicles, like buses and trucks, are allowed a larger output of NOx than cars and light commercial vehicles. The Euro 6/Euro VI diesel standard NOx limits are as follows:



Acceptable NOx level (g/km)

Euro 6

Passenger cars


Euro 6

Light commercial vehicles (≤1305kg)


Euro 6

Light commercial vehicles (>1305–1760kg)


Euro 6

Light commercial vehicles (>1760kg– 3000kg)


Euro VI

Trucks and buses


Non-road mobile machinery directives

SCR technology is also widely used in non-road mobile machinery (NRMM) that uses diesel-powered engines. This varied category of vehicles and machinery can roughly be described as machinery which is not usually seen on the road, and contains such things as hedge trimmers/chainsaws, generators, bulldozers, construction machinery, industrial trucks, forklifts, and mobile cranes.

These engines are subject to a separate EU directive to road-going vehicles: Directive 97/68/EC, which was first introduced in 1999. These regulations stipulate that any diesel engine in this category that is to be produced for the European market must be tested to meet pollutant emission limits. Like the road vehicle directive, it has been amended several times to introduce more restrictive limits for NRMM in line with advances in technology and limits placed on other vehicles and machinery. The regulations apply to new engines to be installed in NRMM, intended and suited to move, or to be moved on the ground, either on or off the road.

As the limits became more stringent with each passing amendment, it became clear that SCR technology was the best technology to achieve the targets. This has meant that AdBlue has become an essential product for NRMM, performing much the same task as it does in road vehicles.

Agricultural tractors

Agricultural tractors and machinery were subject to emissions regulations laid out in EU directive 2000/25/EC, which set out a series of progressively more stringent requirements for the emissions of noxious pollutants from the exhausts of new tractors. There were two new standards, Stage III and IV, which were adopted in 2005, and introduced further reduced limits. Stage III was phased in between 2006 and 2013, while Stage IV came into force in 2014, and is currently still the relevant legislation for newly manufactured vehicles.

This new standard updated the previous ones and incorporated new lower limits for agricultural vehicles into the wider NRMM standards. The lower limits require agricultural machinery manufacturers to make use of SCR technology, as well as Exhaust Gas Recirculation (EGR) and Diesel Particulate Filters (DPF), which can also help to lower NOx and particulate matter (PM) levels in emissions. A new Stage V standard has been adopted too, with plans to introduce it from 2019 onwards.

Which vehicles use AdBlue?

Since the standardisation of EU regulations discussed above, all manufacturers producing vehicles in the EU/EEA have to ensure that their vehicles are tested to meet these acceptable levels. Due to its incredible efficiency, the use of an SCR system with AdBlue is the preferred method for reaching these targets.

If you’ve bought a new diesel vehicle in the last few years since these regulations have come into force, it is highly likely that it will use AdBlue. Even if you do not need it right now, it will probably be a requirement of any new vehicle bought in the future, making it essential to have a working knowledge of the product.

The simplest way to check whether you need AdBlue is to have a look under your fuel cap cover — if there is a secondary, smaller cap that is black or blue adjacent to your main fuel cap, then you will require it. The secondary cap is often labelled with the product name to avoid confusion. Your owner’s manual should also detail if there is a SCR system in your vehicle or not and what exactly needs to be done to maintain it.

How long does a tank of AdBlue last?

The length of time that a full tank of AdBlue will last depends on a number of factors, including what type of vehicle you are driving, your driving style, the length and type of journey, road and weather conditions, and how heavy the load is you are moving. As it is a legal requirement that all diesel emissions must meet the Euro 6 limits, every time you burn any fuel you will be outputting fumes, and therefore AdBlue will be used.

Tank of AdBlue on a truck

© Beademung - licence.

Obviously, if you undertake regular lengthy journeys with your vehicle, such as those undertaken by a long-haul truck driver, you will need to refill your AdBlue a lot more regularly than someone who drives a diesel car just at the weekends. You can conserve your levels by practising efficient driving, which will make sure that you burn through less fuel and less AdBlue.

Your AdBlue should last for at least a few refills of diesel, as only a small amount is injected into your exhaust system compared to the amount of fuel used. After a period of typical use, you should be able to anticipate when you might be in need of a top-up.

How much AdBlue do I need?

When the time comes to refill your AdBlue, the amount that you need will depend on the type of vehicle you are driving. Large trucks and coaches will have a much larger capacity than passenger cars to accommodate the larger volumes of the solution that will be used. If you are only running a car, then a standard 10L pack which can be found at most forecourts will be enough to refill to a comfortable level. A larger vehicle with a bigger tank will require several smaller packs or a larger volume from a barrel, IBC or AdBlue dispensing system.

It is also worth bearing in mind that if you are caught in a pinch with no AdBlue, most vehicles require a minimum amount to be refilled before the engine will function again — consult your owner’s manual or check with your manufacturer for more information.

Should you own or work for a company that owns several vehicles or a large fleet, it would be worth looking into purchasing your AdBlue in larger quantities such as in an IBC or bulk, especially if your vehicles travel regularly over long distances carrying heavy loads. You can save more by buying your own product up front, rather than funding refills as and when they are needed, which will prove costlier.

How can I estimate how much AdBlue I need for my fleet?

When it comes to estimating the amount of AdBlue you will need for a fleet of vehicles, you will have to consider factors like:

  • how far each vehicle will travel,
  • the fuel economy for each vehicle,
  • how many vehicles are in your fleet, and
  • your vehicles’ AdBlue consumption rate.

Van fleet using AdBlue fuel

AdBlue consumption is usually between 2–6% for most vehicles, with diesel vans and lorries tending to inhabit the upper half of this range at 4–6%. Another way to picture this is that for every 100 gallons of fuel burned, 4–6 gallons of AdBlue will be used to reduce NOx levels in the emissions. It is possible to work out approximately how much AdBlue you will need to order for your fleet using a calculation similar to the one in the typical examples below.

Once you have the information about your vehicles and operations at hand, you should be able to work out your own estimation.

Long haul multi-axle lorry (over 25 tonnes)

Average distance of vehicle per month (miles)

Vehicle fuel economy (miles per gallon)

No. of vehicles in the fleet

Fuel consumption per vehicle per month (gallons)

Fleet fuel consumption per month (gallons)

AdBlue consumption rate (%)

AdBlue consumption per vehicle (gallons)

AdBlue fleet consumption per month (gallons)









Medium haul large 2-axle lorry (7.5–14 tonnes)

Average distance of vehicle per month (miles)

Vehicle fuel economy (miles per gallon)

No. of vehicles in the fleet

Fuel consumption per vehicle per month (gallons)

Fleet fuel consumption per month (gallons)

AdBlue consumption rate (%)

AdBlue consumption per vehicle (gallons)

AdBlue fleet consumption per month (gallons)









Short haul light commercial vehicle (< 3.5 tonnes)

Average distance of vehicle per month (miles)

Vehicle fuel economy (miles per gallon)

No. of vehicles in the fleet

Fuel consumption per vehicle per month (gallons)

Fleet fuel consumption per month (gallons)

AdBlue consumption rate (%)

AdBlue consumption per vehicle (gallons)

AdBlue fleet consumption per month (gallons)









Note: These are typical estimates only. Results will vary for different enterprises.

How do I check the AdBlue level in my vehicle?

Thankfully, most new vehicles will have a driver information system on board, which notifies you if there is a particular error or if you are running out of oils or fluids, including AdBlue. This system will usually give you a series of warnings as it becomes depleted, so it is important to get a refill as soon as you can. If you need to check the level of your AdBlue manually, check the owner’s documentation for guidance or contact the manufacturer for further advice.

What happens when my AdBlue runs out?

If you allow your supply of AdBlue to run out, your SCR system will not be able to function, which will lead to limited vehicle performance or your engine not running at all. As your vehicle has been manufactured to meet Euro 6 or VI standards, it is required by law to meet its acceptable emissions level at all times, even when your car has run out of AdBlue. This means that when your SCR system is not able to perform its task, it will prevent you from burning more fuel either by keeping your engine below the threshold or stopping it altogether. This failsafe is in place to protect both the driver and the environment.

How should I store AdBlue?

If you want to keep your own supply of AdBlue, you need to make sure it is kept in the right conditions to maintain its optimum condition. It needs to be kept out of direct sunlight, and between the temperatures of -6°C and 25°C. You should also ensure that the container in which you are storing it is clean and sealed to avoid any chance of contamination that could damage your SCR system upon use.

If you are storing your own AdBlue for large-scale commercial purposes, the likelihood is that you will be keeping large quantities to meet your business need. Although the product is non-toxic, when it is stored in large amounts there are some extra precautions that should be undertaken. This is because urea solutions are harmful to surface and groundwater, as well as having the ability to corrode metals like aluminium alloys, copper, bronze, and iron.

You need to make sure that your container, pipes, and dispensing equipment are all suitable for the storage of AdBlue:

  • Only use storage containers that are high-density polyethylene, polypropylene or stainless steel.
  • Polyisobutylene, free of additives, can be used for seals and hoses. PFA, PVDF and PTFE, also free of additives, can be used as sheet lining for chemical equipment and support rings, as well as seals.
  • Additive-free copolymers of (P)VDF and HFP (viton) can be used for the insulation of wires, seals, and o-rings.
  • Under no circumstances should you use corrosive metals, such as copper, nickel, zinc, or aluminium.

You can find full details of which materials should not be used with AdBlue in the ISO 22241 documentation.

There are a few other measures that you can follow too:

  • Make sure there is a secondary containment measure in place to prevent any spillages from spreading further.
  • Ensure that any essential equipment for clean-up is nearby and ready to use.
  • Make sure any drainage for the dispensing system is separate from any surface water drainage.
  • Regularly test any dispensing equipment, such as a nozzle, to check it is in full working order and won’t jam or remain open for too long.
  • If you have a spill kit ready for use in an emergency, make sure it is one that is compatible with aqueous solutions.
  • Make sure that any staff who will be using the dispensing system are fully trained in case of spillage.

There are no current regulations that govern the storage and handling of AdBlue, but you should look to follow the good-practice guidelines found in the Control of Substances Hazardous to Health (COSHH) to protect yourself, your workers, and the environment from potential spillages.

Does AdBlue have a shelf-life?

Provided that it is kept in the optimal conditions — out of direct sunlight and at a temperature between -6°C and 25°C — your AdBlue can last up to 18 months in storage. If you store it at a higher temperature than this or in a vented container, the shelf-life will only be around 6 months.

How can I keep my AdBlue clean and pure?

As we have discussed, allowing your AdBlue to become contaminated before putting it into your tank can have undesirable consequences for your vehicle’s SCR catalyst. Your solution also needs to be clean so that it can do its job — contaminated AdBlue can reduce its effectiveness at converting harmful emissions, increasing damage to the environment.

Take extra care when handling AdBlue, guarding against contamination at all times. There are many things that can get into your solution and cause problems, including fuel, oil, dirt, and dust, among many others. Try to keep the time that your AdBlue is directly exposed to the environment as short as possible to minimise the risk, and don’t allow anything in the container that shouldn’t be there. If you have to use another container or vessel to transfer the liquid to your vehicle, take extra care to ensure it is clean and has not been used for any other purpose. It is a good idea to keep a set of dedicated AdBlue equipment for this task.

When dispensing AdBlue, take extra care to put it into the right tank — it is not an additive to your fuel and has to be in its own tank to work. Before you begin filling up your vehicle, take a moment to check that the filling equipment you are using is in perfect working order and there are no signs that the solution within has been compromised. Watch out for signs of crystallisation, which can block nozzles on pumps and spouts on jerry cans, increasing the chances of spillage.

We strongly advise against using homemade AdBlue or a urea solution that does not have the AdBlue registered brand name. While the formula used to produce it is quite simple, the quality of the two ingredients is incredibly high. Very pure demineralised water is used alongside uncoated urea that is produced solely for the purpose of AdBlue. Other types of urea are often not up to the task and can cause damage to your SCR system, which can cost a lot of money to fix. In purchasing officially licensed AdBlue, you are also purchasing a product that has been tested and ratified for its exceptional quality.

What should I do if I put AdBlue into my diesel tank?

Firstly, do not start your vehicle, as this could cause damage to your fuel system. If you have put a large quantity of AdBlue into your tank, there is more chance that your vehicle’s fuel system will have suffered harm. Similar to putting petrol into your diesel vehicle, you will need to get the tank drained and dispose of the contents safely before you can refill it. Hopefully there is no lasting damage done, but if there is, you may have to contact your vehicle’s manufacturer to source replacement parts.

What should I do if I put diesel into my AdBlue tank?

The most important thing to remember if this happens is not to start your car. As we have established, diesel can have an undesirable effect on your SCR system, so putting any quantity of it into the tank could cause a lot of disruption. Switching on your engine will cause the diesel to run through the system, potentially compounding the damage. You will most likely need to have your AdBlue tank drained to solve the problem. If there is any lasting damage, you will have to get into touch with your manufacturer to find replacement AdBlue components.


Does AdBlue freeze?

Yes, but the freezing temperature is -11°C, and it won’t begin to freeze until -10°C. As the AdBlue tank on most vehicles is next to the exhaust, while the engine is running you shouldn’t have any problems. Vehicles that have the AdBlue tank situated elsewhere often have a system where it is heated with circulated engine coolant. Even if it does freeze, AdBlue will work perfectly well once it is thawed out.

Rix Petroleum heating oil tanker driving in snow

Although temperatures rarely drop below -10°C in the UK, if you plan on driving your vehicle in a country where the climate regularly reaches this temperature or lower, it may be wise to take a couple of extra precautions:

  • As liquid expands when frozen, leaving some extra room in your tank will give the AdBlue somewhere to expand. This means that if you are running low on the solution, it is better to refill the tank part of the way, rather than to the top.
  • After nights where the temperature has been low, allow your vehicle’s engine to run for a few minutes to allow your AdBlue to warm up and thaw out.
  • Keep any stored AdBlue in a location that is temperature regulated, instead of somewhere where the natural cold can freeze it. If you must keep it somewhere outdoors, you should allow space for freezing expansion in your tank or container.

Is AdBlue flammable or hazardous?

No, AdBlue is not flammable, nor is it considered a hazardous liquid. It is a water-based urea solution, and poses little risk to humans. If you have sensitive skin, it might be wise to wear gloves when handling the liquid to avoid any potential irritation.

You should avoid ingesting or inhaling AdBlue, as you may suffer from an allergic reaction. If you do get AdBlue in your mouth, rinse it out with water and take a few sips afterwards. Inhaling the fumes can sometimes leave some people light-headed, so if this happens, take a few moments to sit down and take in some fresh air while it passes. Eye contact can often cause discomfort — flush your eyes with water if this happens and seek medical attention if the irritation persists.

Where can I buy AdBlue?

If you usually pay for fixed-term servicing of your vehicle, then an AdBlue refill is often included as part of the maintenance. Should this not be the case or you find yourself running out between servicing, you should purchase it from an officially licensed vendor who is registered with the Verband der Automobilindustrie (VDA), the German Association of the Automobile Industry.

It is important to watch out for similarly branded products available for lower prices than officially branded AdBlue — they are often unlicensed and are not manufactured to the high standards of ISO 22241, which is issued by the International Standardisation Organisation (ISO).

Should you need AdBlue during a journey and you aren’t carrying any, you can often find vending pumps at service stations that allow you to refill as much or as little as you need to get on the road again. This option is convenient if you are making a one-off trip, however, if you are running a business that has multiple vehicles making regular journeys, it is definitely worth considering buying in bulk to enjoy the lower prices.

AdBlue from Rix Petroleum

Rix Petroleum is an authorised reseller of AdBlue from Greenchem. We can supply AdBlue in a number of ways to suit your business and fleet requirements. Whether you are just looking to top up your car or searching for a larger quantity to maintain your fleet of trucks, there are a number of solutions that are just right for you.

We can supply the solution in 10L bottles that are perfect for a quick top-up or for keeping in your vehicle in case you have to fill up on the go. We can also supply 200L drums or 1,000L intermediate bulk containers (IBCs), ideal for keeping multiple vehicles well-stocked with AdBlue for an extended period of time. Additionally, if you need a larger quantity, we can provide bulk deliveries too.

To find out how we can help you, simply fill in an AdBlue enquiry form and we will be happy to provide you with more information and a quote. 

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