How AdBlue works

AdBlue Diesel exhaust fluid (DEF) reduces harmful emissions

If your car runs out, it won’t start without a top-up

AdBlue® is a licensed trademark registered by the Verband der Automobilindustrie (VDA). It pertains to car manufacturers and suppliers, mineral and chemical oil companies.

Many diesel vehicles manufactured after 2015 use AdBlue exhaust fluid.

If your diesel cars vans and lorries use an AdBlue tank that needs a top-up at different intervals often between annual servicing.

How often depends on mileage and driving style.

AdBlue Diesel Exhaust Fluid (DEF) reduces harmful emissions and air pollution (in particular, Nitrous Oxides). If diesel cars run dry of AdBlue, the engine will not restart.

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The basics of AdBlue

Carblue provides consumption details based on driving style and annual mileage.

Generic AdBlue top up works for almost all car make and models. It includes:

  • Mannol
  • Redex
  • STP
  • Green Chem
  • Status
  • Carlube
  • Silverhooks

AdBlue prices

Order quickly at low cost via sites like:

Expect prices to range from £11.50 to £39.99 depending on quantity

Consumption is based on driving style and car model.

Diesel drivers can check AdBlue consumption based on the make model and year of car manufacturers or vehicle handbook.

Does my car need AdBlue?

If you need to top up, some filling stations sell although it tends to be expensive compared to:

What is AdBlue?

AdBlue is known by other names including AUS 32 or DEF (Diesel Exhaust Fluid) .

AdBlue is a liquid solution for diesel car fluid systems. It is not a fuel additive.

Diesel cars using AdBlue have a separate tank and filler cap often located next to main diesel fuel filler cap. Some models are refilled from a reservoir kept under the bonnet or boot. See the image below.

AdBlue refill

What is AdBlue made of?

AdBlue is an aqueous urea fluid predominantly made from 67.5% deionised water and 32.5% urea.

What is urea? (Otherwise known as Carbamide organic compound).

What is deionised water – purified water processed to remove impurities.

AdBlue is consumed within SCR (Selective Catalytic Reduction) reducing the high concentration of Nitrogen Oxides (harmful emissions) produced by modern diesel engines.

AdBlue is a non-toxic solution and usually colourless.

How does AdBlue work?

Active emissions control technology

Drops of AdBlue are infused into the exhaust system. When combined with high temperatures a chemical reaction transforms AdBlue into carbon dioxide and ammonia..

Within the SCR catalyst, the harmful nitrogen dioxide gasses are mixed with ammonia and altered to water vapour and nitrogen. It reduces harmful exhaust gases and supports emissions regulations.

What happens if my vehicle runs out of AdBlue?

Modern and new car electronic control units (ECU) have dashboard amber warning light systems that inform when you need to top up. If a car runs out whilst driving, engine performance is reduced to limp mode to lower emissions output. If the engine is switched off, the car will not restart until AdBlue is topped up.

It is therefore essential to refill AdBlue once a vehicle alert is triggered.

Modern selective catalytic reduction vehicles signal as AdBlue is running low, usually within 1,000 or 1,500 miles of driving. 

Certain car manufacturers like Peugeot claim some of the models they produce can travel 12,000 miles (at the time dealer services are due) before needing a refill. However, much depends on driving style and city or motorway driving. 

List of cars which use AdBlue

A diesel vehicle check to manufacturer from  2015 may mechanically rely on AdBlue.

See our AdBlue vehicle Information index and check if a car runs on AdBlue.

Typically, all German and French diesel vehicles use the solution, but so do most Land Rover and Jaguars.

Learn more about car performance

Motorists can also check car details with a registration number. Vehicle reports offer CO2 output, emissions and road tax charges.

Does my car use AdBlue?

See our quick guide and check if a car needs AdBlue. If we don’t list a make or model for top-up, use these steps:


  • Look for the AdBlue refill cap under the bonnet, in the boot or next to the diesel filler cap.
  • Check the vehicle handbook or run a search on the internet using vehicle make/model otherwise, call up the local dealer.
  • The name in a car model is another giveaway, i.e. VW Golf Bluemotion etc. Any mention of ‘Blue’ in a vehicle name pertains to AdBlue.

Where to buy AdBlue?

Standard AdBlue works in most types of car – there is no need to buy AdBlue by make and model.

Good brands include STATUS, Carlube and LANDOWNER

Lowest prices are found on AdBlue can be purchased at most petrol stations, accessory shops like Halfords and supplying dealers. Some garages offer AdBlue by pump.


Buying AdBlue by quantity

Containers are typically available in 1, 5, 10 and 15 litres. We recommend buying a bottle that includes an attached spout neck for easy application.

It’s not necessary to carry AdBlue in a vehicle. The AdBlue warning system will provide notice when it’s running low.

AdBlue prices – how much does it cost?

Businesses and commercial enterprises with a fleet of vehicles to manage buy AdBlue in bulk and usually store on-site.

For private motorists, a 5 to 10 litre drum of AdBlue is all that is needed. AdBlue is not expensive to produce although transportation can be costly.

Buy 10 litres of AdBlue diesel solution for around £12 to £15 delivered. Amazon offer the keenest prices with next day delivery.

See the range listed here

How long does AdBlue solution last?

Driving style and mileage dictate how much AdBlue is consumed.

Broadly speaking, UK motoring consumption is around one litre of AdBlue per 650 miles. Again, this figure depends on the make and model of the car and how quickly a vehicle is driven.

The miles per gallon provide an indicator as to how quickly AdBlue is consumed. In some instances, AdBlue can be consumed at a rate of 1 litre per 400 miles.

Different makes and model of car have varying tank sizes. For some vehicles, a refill may be required every 4,000 miles whilst those with larger tanks are topped-up every 14,000 miles.

Averaging 10,000 miles per year most drivers will need to top-up AdBlue at least one-time between annual or biannual service schedules.

AdBlue warning lights – best-practice motoring

Is it mechanically safe to drive a vehicle with AdBlue warning status?

It is generally safe to continue driving after a vehicle has alerted to a low-level of AdBlue. But motorists must top-up in good time. recommend refilling a maximum of 300-miles after a vehicle has altered to low-levels of AdBlue.

How to reset the AdBlue warning module by make and model

The Electronic Computer Unit (ECU) will reset AdBlue warning alerts. To enable this:


  1. Top-up AdBlue
  2. Start the vehicle
  3. Run for a few seconds and then switch off the engine and ignition.
  4. Restart the vehicle to reset the AdBlue warning light

What happens if AdBlue is put in the diesel tank?

Do not start the vehicle or even start the ignition (as this draws fluid into the fuel pump).

The fuel tank must be drained and cleaned before the engine is started again else the solution will damage injections and the fuel pump.

Breakdown services like Green Flag, RAC and AA can help.

If diesel is put into the AdBlue tank

Do not switch on the ignition or start the vehicle else the Selective Catalytic Reduction will become damaged and need replacing.

Contact a local mechanic or breakdown service so fuels and solutions are drained from the vehicle.


How to top-up AdBlue

Each make and model of the car will have their own procedures to top-up the AdBlue solution. We recommend checking our application list below:


  • Read the vehicle handbook instructions. It provides simple instructions on how to add AdBlue, including quantity.
  • If a vehicle has run dry of AdBlue add a minimum of 5-litres before restarting the engine.
  • Many AdBlue bottles include an attachable spout for easy pouring otherwise a funnel is needed.
  • AdBlue is a non-toxic solution, but spillages and contact with skin or eyes must be thoroughly washed off.
  • AdBlue should also be washed away from car bodywork and trim.

How does AdBlue work at reducing emissions?

At high temperatures, AdBlue is mixed with exhaust fumes. This reacts with nitrogen oxide fumes (NOx gas) from the engine resulting in a breakdown of harmful gasses into nitrogen and water vapours.

What is NOx exhaust gas?

NOx gasses are poisonous and cause serious health problems. They also impact the environment by the formation of particulate matter, acid rain, ground-level ozone, and dirty smog air.

Vehicles need to meet exhaust gas emissions thresholds within Euro 6 standards.

Selective Catalytic Reduction (SCR) systems enable most vehicles to meet Euro 6 standards. The SCR processes AdBlue and reduces its harmful gasses.

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