In this article, you learn some things about AdBlue like: here’s how it works, how much it costs, and what is the urea solution for on modern cars with SCR system.

Many car drivers discovered AdBlue (or urea) only after buying the car. An extra liquid to add from time to time, only with more attention not to run out of it to avoid staying on foot. Since not everyone knows exactly what it is, what it is for, how much it costs and why AdBlue needs to be added to the car, let’s clarify a bit. Let’s dispel the myths and bar tips on the correct use and refilling of urea or AdBlue , code name AUS32.


With the Euro 6 emission limits (nitrogen oxides NOx of 80 mg/km) car manufacturers realized that the EGR valve alone would not be enough. In some cases, it has been thought of multiplying the EGR valves on the exhaust line. For many other cars, it was not possible to avoid using the SCR system from Euro 6C. The need to add AdBlue in a dedicated car tank in the same way as for fuel is linked to the presence of the SCR (Selective Catalytic Reduction) system. 

SCR (Selective Catalytic Reduction) system → ADBLUE SYSTEM EXPLAINED PHENOMEN



AdBlue is a mixture containing 32.5% technical urea and 67.5% distilled water. AdBlue is therefore only the name held by the VDA (the Association of German Car Manufacturers) for the AUS32 (Aqueous Urea Solution 32.5%) mixture which must comply with the specifications of the ISO 22241 . You will have to pay attention to this detail when it is necessary to top up AdBlue, since one brand is as good as another, as long as it respects the aforementioned standard. In fact, according to various countries, AdBlue (or rather AUS32) can become commercially DEF in America or Arl32 in Brazil. Since there is no AdBlue without SCR, modern engines that use this nitrogen oxide reduction system also have a dedicated injector on the exhaust line. Based on the request from the engine control unit and in specific operating and temperature ranges, an amount between 3 and 5% of AdBlue is injected with respect to the diesel consumed, which activates the NOx reduction reaction, transforming them into nitrogen and water vapor in addition. to other gases produced by combustion.



The AdBlue consumption is so limited (something about 1-1.5 liters per 1000 km) that should not be topped up so frequently. Depending on the car, the AdBlue tank can hold between 10 and 20 liters (my DUSTER II seems to have it 19l ). And we come to the first myth to dispel: if you are used to topping up the radiator levels with water only, know that altering the exact concentration of urea in AdBlue reduces the of the catalyst. So better not to improvise home solutions or top up with water only to deceive the engine block, as the cost could be much more expensive in the long run than the cost of about 1,5 euro per liter of AdBlue by RENAULT.


We talk about refilling as if it were child’s play, but isn’t it harmful to handle AdBlue? Don’t worry, we are not crazy, AdBlue can be handled without particular risks – unlike the wax used with some particulate filters – read here, which must be handled only by trained technical personnel and with precautions. To top up the AdBlue, just locate the filler, usually next to the fuel filler, but smaller, in the trunk, or in some cases in the engine compartment. But where is AdBlue found? With the spread of more and more cars with SCR system AdBlue is easy to find in any car parts shop. The driver always receives a message from the on-board well in advance when he still has around 1000-2000 km of range. Unless there is a problem with the AdBlue system .


To make life easier for motorists who are often on the road and are not very familiar with DIY and topping up, there are many petrol stations that are equipped with specific pumps to top up the AdBlue ( check here the map of the Italian distributors that supply AdBlue ), but you have to take into account a cost per liter higher than the 1-1.5 euros that you would pay by refilling the AdBlue purchased at a dealership or from an authorized auto parts dealer yourself. It’s not all pink as it looks though. While the risk associated with AdBlue toxicity is practically nil, it stinks, can stain clothes, and damage paint. Furthermore, the freezing point at -11 ° C seems to have already put a strain on frozen cars if the AdBlue tank was not properly repaired. Result: the car is blocked until the AdBlue solution has returned to a liquid .

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