7 Things You Need to Know About AdBlue (2021)

7 things you need to know about Adblue (2021) in white text over an image of an Adblue tank and diesel tank on a car

Diesel drivers need to know about AdBlue. Not only does it play an important role in keeping your exhaust emissions under control, but you won’t go anywhere without it!

AdBlue may sound complicated, but it’s actually quite simple. Here are the 7 main things to remember about AdBlue, including how it works, when to top up and how you can buy it.

AdBlue is a Diesel Exhaust Fluid

That’s DEF for short. It’s a colourless liquid stored in a separate tank, usually next to your diesel tank. If you don’t know where yours is, your vehicle handbook will help you to find it on your car.

Most importantly, it is NOT a fuel additive. Mixing AdBlue and diesel can be a very costly mistake. If you suspect they have mixed in the same tank, DO NOT start the car. Call your recovery provider and get them to tow you to a garage where a mechanic can assess the damage.


Adblue tank in diesel car
This is the most common location for the AdBlue tank. Although it may be next to the full tank, you definitely shouldn’t mix the two!

AdBlue is Made of Water and Urea

This Diesel Exhaust Fluid contains 2 parts deionised water and 1/3 concentrated automotive urea (made of Ammonia and Carbon Dioxide). AdBlue is non-toxic, perfectly safe and a special mixture created for chemical reactions.

It is not, as some people claim, made of pig urine or pure urine.

Each different type of AdBlue has a different International Organisation for Standardisation (ISO) 22241 number. This is to ensure the quality and effectiveness of the Diesel Exhaust Fluid. Modern diesel cars run on ISO-22241-1, -2 or -3 AdBlue.

Diesel Exhaust Fluid Reduces Harmful Exhaust Emissions

In late 2015, the EU introduced their strictest emissions standard yet: Euro 6. This targeted diesel vehicles in particular because they naturally produce more CO2 and Nitrous Oxide (NOx) than petrol vehicles.

These are the main gases choking the environment, and cause an excess 40,000 deaths in UK cities each year!

The solution to this problem was reducing the exhaust emissions at source. This involves AdBlue and another diesel specific part, the Diesel Particulate Filter.


exhaust pipe with white smoke emitting exhaust emissions, reduced by AdBlue and DPF cleaning
Keep your exhaust emissions low and reduce the risk of an MOT failure by booking a DPF flush and AdBlue top up today!


Your vehicle carefully injects AdBlue into the exhaust gases produced by your engine. The ammonia in the urea breaks down the NOx emissions through a series of chemical reactions. This means your exhaust releases Nitrogen and water vapour into the atmosphere instead.

In fact, AdBlue can reduce your NOx emissions by up to 90%!

However, it’s not yet fitted to every diesel car. The extra weight of the tank makes it too big and too expensive to fit on smaller diesel cars. At the time of writing, it is only fitted to diesel vehicles with 1.6 litre engines and above.

This means a 2016 Volkswagen Polo 1.4 TDI is as toxic as an HGV. A Leeds University study found that the Polo produced 1.2g of NO2 per kilometre travelled – the same as a fully laden, 13-litre engine diesel lorry.


A 2016 VW Polo produces as much NO2 per kilometre travelled as a 13-litre diesel lorry!


Given these shocking statistics, it’s no surprise that more people are considering whether they should buy a diesel car. If you do own one, it’s your responsibility to keep it as environmentally friendly as possible.

That means keeping your DPF clean at all times. This traps soot produced during diesel combustion, but can sometimes struggle to ‘regenerate’. This is the process of burning the soot off.

If your DPF gets too blocked, it can be very costly to replace. The repair can cost £1,000 for some vehicles! However, a blocked DPF or lack of AdBlue can lead to your vehicle failing its MOT test. There has been a 240% rise in emission related MOT failures for diesel vehicles since 2019. This leads to the stress of organising a DPF repair quickly and without comparing prices to get the best deal.

Don’t let it get to this point. Book a DPF flush with BookMyGarage instead. Prices start from £99!



Reduce your carbon footprint and book a DPF Flush today! Prices start from £99



Your Car Will Break Down Without a Top-up

AdBlue is integral to diesel vehicles. This means your car treats it like fuel and won’t run without it.

While the engine won’t cut out as dramatically as it would if you run out of fuel, it will enter ‘limp home’ mode. This limits your vehicle’s power and performance, allowing you to get home or to a garage safely. However, once you switch the engine off, it won’t restart until you fill up your AdBlue tank.


man stood by broken down car on desert road on beautiful day
Don’t get stranded in the middle of nowhere because you run out of AdBlue. Top up in plenty of time with BookMyGarage! Photo by Jamie Street on Unsplash

The Warning Light Means You Are Close to Running Out of AdBlue

If your car does break down due to a lack of AdBlue, you can’t claim you weren’t warned. Your dashboard will start showing this warning light (pictured below) when you have about 1,500 miles fluid left. That gives you plenty of time to top up your tank.

AdBlue warning light
Look out for this AdBlue warning light.


But what is the easiest way to buy AdBlue near you?

Buy AdBlue Near You With BookMyGarage

The answer is always BookMyGarage. Our UK garage network offers efficient AdBlue top-ups near you! Just enter your reg number and postcode into our online booking tool to instantly compare thousands of independent, franchise and fast-fit garages near you. Filter by reviews, price, availability or distance to find the best deal for you.

And the best part is, our AdBlue prices are very affordable!

You can buy AdBlue for just £20, up to 10 litres. That’s more than enough for a full tank, and you get an expert mechanic to do the work for you. That way, there’s no risk of accidentally mixing AdBlue and diesel!

Book your top-up online through BookMyGarage now, and avoid a stressful breakdown when your car runs out of Diesel Exhaust Fluid.



Book your top up for just £20, up to 10 litres, now



You Should Top Up Every 5,000 Miles

This is the best mileage because the average AdBlue tank is between 10 and 11.5 litres, and 1 litre of AdBlue lasts around 600 miles.

5,000 miles might seem a bit safe, but remember what happens if your car runs out of AdBlue. If you book an appointment after 5,000 miles, you still have a safety net if it doesn’t fit in with your schedule straight away.


Book an AdBlue top-up every 5,000 miles to leave around 1,000 miles to get the service done. With this Diesel Exhaust Fluid, it’s better to be safe than sorry!


Diesel Cars Need AdBlue as Much as Fuel

This Diesel Exhaust Fluid is very important because it keeps your vehicle’s emissions as low as possible. That’s why your car won’t go anywhere without AdBlue.

Make sure to buy AdBlue through BookMyGarage every 5,000 miles to avoid the stress of an expensive breakdown. Enter your reg number and postcode now to book a top-up near you now. It’s only £20 for up to 10 litres. Compare. Save. Job Done.



Buy AdBlue Near You Now!

Mandy Weston

Mandy Weston

Mandy is an ex-mechanic, with 22 years’ experience in the motor industry. As an in-house motoring expert, Mandy is the go-to woman for any relevant questions that our customers have; both garages and drivers. From specific problems with your car to general maintenance, Mandy is a reliable source of information and advice. Her passion for motoring is a huge factor to her success and the huge wealth of knowledge that she has. She now uses her remarkable grasp of the industry to write regular content for our readers to help drivers understand their car better, avoid being ripped off by garages and save money on their motoring requirements.