UPDATE: AdBlue market has matured and prices have stabilised. At the moment the most expensive AdBlue is most likely to be found at your local garage (well over £20 for 10 litres), while the most competitive prices are offered by numerous sellers through amazon (around £18 for 20 litres, including delivery).

AdBlue is a fuel additive for Euro 6 diesel vehicles fitted with a selective catalytic reduction (SCR) system. Selective catalytic reduction removes oxides of nitrogen (NOx) from a vehicle’s exhaust gases. AdBlue is automatically injected into the exhaust gas of a diesel vehicle, in front of the SCR catalyst, downstream of the engine – it is not mixed with diesel fuel. Heated in the exhaust it decomposes into ammonia and CO2. When the diesel exhaust NOx reacts inside the catalyst with the ammonia, the harmful NOx molecules are converted to harmless nitrogen and water.

What are the ingredients of AdBlue?

AdBlue is a 32.5% solution of high-purity urea in de-mineralized water that is clear, non-toxic and safe to handle. It is non-explosive, non-flammable nor harmful to the environment.

Do I need to buy it?

If your Euro 6 diesel vehicle features SCR technology, then yes. You need to top up the AdBlue tank regularly. Most passenger vehicles with SCR are fitted with 6 to 15 litre AdBlue tanks. Running out of AdBlue will prevent the engine from starting up.

How much AdBlue do I need? How much AdBlue will my car use?

In general, consumption of AdBlue in passenger vehicles is on average 5% of diesel use, but it can vary significantly. Therefore, for every 60 litre tank of diesel a vehicle will use up to 3 litres of AdBlue, and this can significantly add to the overall car running costs. AdBlue consumption varies widely between manufacturers and engines.

Depending on vehicle engine size and driving style it may be necessary to top up AdBlue anywhere in between 2500 miles and 15000 miles. AdBlue consumption is directly related to the exhaust gas NOx levels, and these depend on many variables: winter or summer diesel fuel mix, ambient temperature, engine temperature, city vs motorway driving, etc.  Its consumption is not completely proportional to diesel consumption.

Where can I buy AdBlue?

AdBlue is widely available from main dealers and independent garages, as well as online shops and accessory shops and chains in 1, 4, 10 litre containers with and without AdBlue spouts. Hint: you do need the AdBlue spout.

Prices vary significantly, from around £0.70 per litre to up to £4 per litre, so it pays to shop in advance.  A number of online retailers also offer 10 litre AdBlue refills – anything around £10 for 10 litres of AdBlue, including delivery, is a good price. 10 litres for less than £10 delivered is a steal. Avoid having to buy 10 litre containers from motorway service stations – most charge around £25, or more, for 10 litres.

In general, best prices are offered at lorry petrol filling stations where it’s available from AdBlue pumps, right next to diesel pumps. However, AdBlue pumps that exist in many petrol stations for commercial vehicles feature fluid flow rate that may be too high for a passenger cars, and are therefore fitted with a magnetic stop valve, so filling up a passenger car may not be possible.

Topping up AdBlue in late model vehicles is very easy, as the AdBlue filler is usually located next to the diesel filler. Some older vehicles, however, may feature AdBlue fillers inside the boot or under the engine bonnet, making topping up a little tricky.