You may have heard of AdBlue if you've owned or driven a diesel car since 2015 or an HGV since 2009. But do you know why it's added to a diesel vehicle? Don't worry if the answer is no. That's why we're here to help. 

In this blog, we'll discuss what AdBlue is, what it is used for, what it's made from, the typical AdBlue injector replacement cost in the UK, and whether your car needs AdBlue. No stone will be left unturned! Scroll down to become an expert ASAP.  

What is AdBlue?  

AdBlue is a liquid that reduces harmful emissions in diesel cars. It is stored in a separate tank, similar to the fuel tank, and requires filling, either by the driver or as part of a maintenance service. 

Fun Fact: It’s actually called Diesel Exhaust Fluid (or DEF) as AdBlue is a brand name.

Why is AdBlue needed?  

AdBlue is needed because it reduces nitrogen oxides (NOx) from a car’s exhaust pipe.  

The Euro emissions regulations are updated every few years to improve the air quality around Europe. In 2015, the newest regulation, Euro 6, came into effect.  

This new set of regulations came with more stringent rules on the harmful emissions diesel-engined cars are allowed to emit, particularly NOx. This is a factor in clear air zones worldwide, including London’s Ultra Low Emission Zone (ULEZ). 

AdBlue reduces the level of these pollutants by acting as a catalyst inside the SCR (Selective Catalytic Reduction) system to ensure as much Nox is burned off and transformed into harmless water and oxygen.  

What is AdBlue made of?  

AdBlue is a liquid that consists predominantly of water and urea in roughly a 70/30 mix. Other additives and chemicals are added to stabilise and colour the fluid.  

Is Adblue made of pigs' urine?  

No. AdBlue is not made from pigs’ urine – this is a common myth. The urea added to make the product is entirely synthetic.   

Whilst urea is present in urine from all animals, humans and pigs included, no animal by-products are used in making AdBlue.  

The main reason is that the SCR system is extremely sensitive to impurities. The extra compounds found in urine would cause many issues with your car's exhaust system.  

How much does the AdBlue injector replacement cost in the UK? 

An AdBlue injector replacement cost in the UK costs between £120 to £160. 

However, this cost can be affected by how many fuel injectors your car needs and what type of car you have. The cost can also vary from country to country. So, make sure you're looking at prices for the right country.  

What is AdBlue used for?  

The SCR system in diesel cars was introduced to reduce the emission of Nox pollutants. It does this by combining an exhaust fluid, with the stream of hot exhaust gases inside a catalytic converter.   

AdBlue is one of the most common DEFs (Diesel Exhaust Fluids) and is fed from a separate tank, usually stored near the diesel tank, to be injected into the exhaust.   

When operating properly, an SCR system (Selective Catalytic Reduction) combined with an EGR (Exhaust Gas Recirculation) system can reduce harmful Nox emissions by up to 90%  

What happens if you run out of AdBlue?  

If you run out of AdBlue, the engine’s performance and power will be limited to reduce emissions.  

Cars that require the addition of AdBlue do so because their SCR systems cannot function without it. Any diesel car made after 2015 is allowed to exhaust a certain level of Nox pollution.   

Many cars, therefore, will go either into a reduced power mode, also known as a limp home mode or refuse to start together if no AdBlue is present.  

That is why keeping a small bottle in your car and other essentials is a good idea, just in case you’re caught short.  

How much AdBlue will my car use? 

Cars use AdBlue at different rates. Most need to travel several thousand miles to use an AdBlue tank. Some can even travel up to 10,000 miles before running out.  

In contrast to a common myth, AdFuel doesn’t burn extra fuel. Your fuel usage will remain the same as normal, even when using this product. 

What happens if you put diesel in an AdBlue tank?  

Fuel will be injected into the exhaust catalyst system, and your car will be damaged.  

This is a costly mistake, as diesel Exhaust Fuels are specifically designed to be used in a separate system from regular diesel fuel. The AdBlue should not enter the engine under any circumstances.   

AdBlue tank filler caps are often located in the fuel filler door. The filler hole is too small to allow diesel to be put in, but an AdBlue bottle could be put into the diesel tank.

If you accidentally put AdBlue in your diesel tank, call your emergency roadside assistance as soon as possible, and don’t drive the car more than absolutely necessary.   

A small amount of AdBlue could probably be diluted into the fuel to cause no issue, but it’s best to get a professional opinion in your particular situation.   

Related Reading: How To Know If DPF Is Blocked  

How often do you need to fill up AdBlue?  

You only need to buy and refill your AdBlue once yearly for the average car travelling 9-10,000 miles a year.  

Although different cars use different amounts of AdBlue, a typical tank will hold 15 litres of fluid and should last around 9,000 miles.   

If you’re worried about your AdBlue levels and aren’t sure what to do, you can easily take your car for an interim service where they will perform all the basic checks and look after your levels.  

Can you refill AdBlue yourself?  

Yes, you can fill your car with AdBlue yourself. Two main systems on vehicles are fitted with AdBlue: user-fillable and service-filled. 

To fill it yourself, you must use the separate filler cap for AdBlue, which is usually located next to the main diesel filler, in the boot, or sometimes in the car bonnet.  

Some other cars have a hidden filling system, usually under the boot carpet. These systems are designed to be filled by the service centre at your regular service intervals.   

Does my car need AdBlue? 

Your car will show an alert on the dashboard display or system screen if it needs an AdBlue refill. 

If you’re unsure of which system your car uses or are borrowing or renting a car and the owner didn’t tell you whether to add in AdBlue, there are several key things to look out for:  

• An AdBlue cap near the fuel filler  
• The car model has ‘blue’ in the name, such as Mercedes BlueTEC, or VolksWagen’s BlueMotion  
• The handbook notes the AdBlue filler location  
• The onboard computer will advise when the AdBlue tank needs to be refilled  

How to reset an AdBlue warning 

You can reset an AdBlue warning alert by refilling the AdBlue tank. Once complete, the alert should disappear. If it doesn’t, drive for a few miles to allow the system to reset.  

If the warning doesn’t disappear after 10 miles, there might be an issue with the AdBlue sensors. Your vehicle’s manual should have more information about this. But if not, you should schedule an appointment with a mechanic. 

Which cars use AdBlue? 

Most diesel cars that meet Euro 6 standards need AdBlue. However, some of them rely on alternative systems to reduce NOx emissions.  

You can figure out if your car uses AdBlue by looking for the word “blue” or the letters “SCR” on your car’s manual. For example, Fords have an EcoBlue badge, Citroen diesels are named BlueHDi, and Volkwagons are called TDI SCR.  

If you can’t see Blue or SCR in the car’s information, check your fuel filler car for an AdBlue filler.  

Still trying to figure it out? Reach out to your dealer or manufacturer for a clear answer. 

Do petrol cars need AdBlue? 

No. Petrol cars don’t use AdBlue. This formula is only designed to reduce diesel emissions.  

Does AdBlue harm the environment? 

Nope! AdBlue is not flammable or toxic and doesn’t harm the environment.  

That being said, you should still avoid touching it as it can irritate your skin. If spilt, dilute it with water and mop or wipe it up. You should clear AdBlue as soon as possible as it can be corrosive to some metals and plastics.  

AdBlue: The bottom line 

Using AdBlue is a normal part of life as a diesel driver. However, if you’re new to diesel vehicles, it can be a little confusing. Hopefully, this guide has familiarized you with what AdBlue is and how it works. Save this page so you don’t lose any information! 

Need to speak to an expert? 

Spread the cost of car repairs into interest-free instalments with 1000s of trusted repairers. 

Author - Joseph Law

Joseph has been writing about cars for over seven years and writing for Bumper for over two, blending his passion for automobiles with a talent for storytelling.

Joseph has written about engineering and cars for Autozilla, Komaspec, and several engineering manufacturers. When he's not writing or tinkering with one of his five cars, Joseph dreams of owning an Alfa Romeo 33 Stradale.