AdBlue & DPF What is AdBlue

What is AdBlue made of?

Q: What is AdBlue made of?

AdBlue is made from 32.5% high-purity urea and 67.5% deionised water. It is injected into the exhaust system of diesel vehicles to convert harmful nitrogen oxide (NOx) emissions into harmless nitrogen and water vapour using a process called Selective Catalytic Reduction (SCR).

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AdBlue is a non-toxic fluid made from 32.5% high-purity urea and 67.5% deionised water. It is injected into the exhaust system of diesel vehicles to chemically convert harmful nitrogen oxide (NOx) emissions into harmless nitrogen and water vapour.

The Two Ingredients in AdBlue

High-purity urea: The urea used in AdBlue is pharmaceutical-grade and must meet strict ISO 22241 standards. It is not the same as agricultural urea fertiliser, which contains impurities that would damage your SCR system. 2

Deionised water: Ordinary tap water cannot be used because its mineral content would block and corrode the SCR catalyst. The deionised water in AdBlue is specially purified to remove all ions and minerals. 3

Precise ratio matters: The 32.5% urea concentration is not arbitrary — it is the exact ratio at which the solution has the lowest freezing point (around -11°C), making it practical to use in real-world conditions. 2

How AdBlue Works in Your Engine

Selective Catalytic Reduction (SCR): AdBlue is stored in a separate tank and sprayed into the exhaust gases before they reach the SCR catalyst. The heat converts the urea into ammonia, which then reacts with NOx to produce nitrogen and water. 3

Significant NOx reduction: SCR systems using AdBlue can reduce NOx emissions by up to 90%, making them the primary technology used by manufacturers to meet Euro 6 emissions standards. 2

Required on modern diesels: Most diesel cars, vans, and lorries built after 2015 use AdBlue as part of their emissions control system to comply with Euro 6 legislation. 4

What AdBlue is Not

Not a fuel additive: AdBlue never enters the engine or fuel tank. It has its own dedicated filler cap and reservoir, usually located near the fuel filler, in the boot, or under the bonnet. 3

Not interchangeable with cheap alternatives: Using non-ISO-standard urea solutions or tap water mixtures will damage your SCR system and could trigger a warning light or prevent the engine from restarting after refuelling. 2

Keeping Your AdBlue Topped Up

Consumption rate: Most cars use roughly 1 litre of AdBlue per 600–900 miles, though this varies by vehicle and driving style. Your dashboard will warn you when levels are low. 3

Where to buy it: AdBlue is widely available at petrol stations, motor factors, and online. Prices per litre vary considerably between forecourts, so it pays to check before you stop. 1