AdBlue is a diesel exhaust fluid made from 32.5% urea and deionised water. It is injected into the exhaust system of modern diesel vehicles to convert harmful nitrogen oxide (NOx) emissions into harmless nitrogen and water. Most diesel cars built after 2015 require it, and running out can prevent the engine from restarting.

AdBlue & DPF What is AdBlue

What is AdBlue?

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AdBlue is a non-toxic exhaust fluid injected into the exhaust system of modern diesel vehicles to break down harmful nitrogen oxide (NOx) emissions into harmless nitrogen and water. It is required in most diesel cars, vans, and trucks manufactured from around 2015 onwards that use Selective Catalytic Reduction (SCR) technology.

What AdBlue Is Made Of

Simple composition: AdBlue is a precisely mixed solution of 32.5% urea and 67.5% deionised water. It is non-flammable, non-toxic, and classified as a safe fluid to handle. 2

Not a fuel additive: AdBlue is stored in its own dedicated tank, completely separate from the diesel tank. You must never add AdBlue to your diesel fuel or vice versa. 3

How AdBlue Works

SCR technology: AdBlue is sprayed into the exhaust stream before the catalytic converter, triggering a chemical reaction that converts toxic NOx gases into harmless nitrogen and water vapour. 2

Emissions compliance: The system allows diesel vehicles to meet Euro 6 emissions standards, which set strict limits on NOx output from passenger cars and commercial vehicles. 4

Engine shutdown risk: If your AdBlue tank runs empty, most modern vehicles will not restart once the engine is switched off. Warnings typically appear when around 1,500 miles of fluid remain. 3

Which Vehicles Use AdBlue

Most post-2015 diesels: The majority of diesel cars, SUVs, vans, and HGVs built after 2015 use AdBlue as part of their SCR exhaust treatment system. Check your handbook if you are unsure. 2

Not required in petrol cars: AdBlue is exclusively a diesel technology. Petrol, hybrid, and electric vehicles do not use it.

MOT implications: A tampered or removed SCR system will result in an MOT failure, as exhaust emissions are tested at every inspection. 4

Topping Up and Running Costs

Consumption rate: A typical diesel car uses roughly 1 litre of AdBlue per 600–1,000 miles, though this varies by engine size and driving style. 3

Where to buy it: AdBlue is widely available at petrol stations, motor factors, and supermarkets. Prices vary, so it pays to compare before you top up. 1