What is AdBlue and Does My Diesel Car Need It?

Last updated October 24th, 2022

Introduced in 2014 and made mandatory in September 2015, the Euro 6 emissions standards set new regulations that car manufacturers had to follow. These included a required 67% drop in nitrogen oxides.

To meet this challenge, some manufacturers began to adopt an exhaust fluid commonly known as AdBlue to break down the nitrogen oxide gases, making them less harmful before they are emitted from the exhaust.

AdBlue is a mixture of urea and deionized water that is stored separately to the diesel fuel tank. It works in vehicles with SCR technology, which many car manufactures have implemented to comply with Euro 6 regulations.

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Which cars need AdBlue?

Not all diesel cars require AdBlue – but many manufactured from 2014 onwards do. Some diesel manufacturers did not adopt the SCR technology straight away, although most diesel cars produced after September 2015 utilise SCR. You can check whether your car has an SCR system by referring to the owner’s handbook.

You should keep your car topped up regularly to ensure that harmful emissions are not released into the environment and should do so when instructed by the car. It is also likely that your AdBlue will be topped up by a mechanic at each service interval.

How do you top up AdBlue?

AdBlue can be purchased at most car retailers, petrol and service stations - or online. Petrol stations have dispensers for AdBlue with different nozzles for HGVs and cars. The price of AdBlue will vary depending on where you purchase it from, but you can expect to pay around £1.50 per litre from a bottle or £0.60 per litre if you get it from a petrol station nozzle.

Most manufacturers have a different cap for adding your AdBlue, which can be found next to the fuel cap. It will always be blue to avoid confusion between where you should add fuel and where you should top up your AdBlue. If you cannot find where to add your AdBlue, check your owner’s handbook to confirm whether your car needs it. If it does, the handbook should also specify where it needs to be added.

How often should you top up AdBlue?

How often your car needs to be topped up with AdBlue depends on your driving habits, the distance driven, the type of roads you are driving on - and the environmental conditions. This will determine whether you need to top up between services and MOTs or periodically, at the garage.

What happens if your car runs out of AdBlue?

If your car is running low on AdBlue, you will most likely see a warning light appear on your dashboard to make you aware it is due for a refill. On most cars, this warning will illuminate when you have around 3 litres left in the tank, which will give you up to 1,500 miles of driving before it runs out. This warning light will not go out until you have refilled your AdBlue.

If you choose to ignore this low-level warning and continue to drive your car, the number of emissions your car emits, and the performance of the vehicle will be affected. If you allow it to get to empty, your car will not turn back on once it is turned off, until it is refilled with AdBlue.