AdBlue & DPF What is AdBlue

What is AdBlue used for?

CheckFuelPrices Editorial Expert Written • 4 industry sources

Reviewed by Jonathan Mathews VERIFIED

LinkedIn Articles 5+ Yrs Peer Reviewed

AdBlue is a diesel exhaust fluid used to reduce harmful nitrogen oxide (NOx) emissions from diesel engines. It is injected into the exhaust system where it chemically converts NOx into harmless nitrogen gas and water vapour.

How AdBlue Works

Selective Catalytic Reduction (SCR): AdBlue is sprayed into the exhaust stream before a catalyst, triggering a chemical reaction called Selective Catalytic Reduction that breaks down toxic NOx gases. 2

What it's made of: AdBlue is a solution of 32.5% high-purity urea and 67.5% deionised water. It is non-toxic and non-flammable but must not be mixed with diesel. 3

Separate from diesel: AdBlue is stored in its own dedicated tank — separate from the fuel tank — and has its own filler cap, usually marked in blue. 2

Which Vehicles Use AdBlue

Most modern diesel cars and vans: AdBlue is fitted to the majority of diesel passenger cars, vans, and trucks manufactured after around 2015 to meet Euro 6 emissions standards. 3

Not fitted to all diesels: Older diesel vehicles and some smaller engines use alternative emissions strategies and do not require AdBlue. Check your vehicle handbook to confirm. 2

Emissions compliance: SCR systems using AdBlue are one of the primary technologies used to meet strict NOx limits under Euro 6 regulations, which are enforced during MOT testing. 4

What Happens if AdBlue Runs Out

Warning lights appear first: Your dashboard will display a warning when AdBlue is low, typically giving you around 1,000–1,500 miles to top up before a further warning appears. 3

Engine may not restart: If AdBlue runs completely dry, many vehicles are programmed to prevent the engine from restarting to avoid breaching emissions regulations. 2

Top up promptly: AdBlue is widely available at petrol stations, motor factors, and online. Consumption is roughly 1 litre per 600 miles, though this varies by vehicle. 3

AdBlue and Running Costs

An additional running cost: AdBlue is an ongoing expense for diesel drivers, typically costing £1–£2 per litre. A 10-litre top-up is usually enough for several thousand miles. 1

Factor in your total fuel spend: If you drive a diesel, keeping on top of both fuel and AdBlue costs matters. CheckFuelPrices shows live diesel prices near you so you can fill up cheaply and reduce overall running costs. 1