Why does the diesel need AdBlue to pollute less?


Engine BlueHDi PSA Group with SCR technology

diesel most modern must comply with Europe’s Euro 6 legislation, which limits to 80 mg/km the amount of oxides of nitrogen (NOx) that exit through the exhaust pipe. In the laboratory have met all, but outside of him there: someone has done wrong calculations, and in virtually all brands of cars.

There are several ways to reduce NOx emissions, but one of the most effective is spraying urea into the exhaust gases, so that the influence on the engine is void. It is a solution of urea 32.5% in demineralized water, commercially known as AdBlue. No, it is not simple urine on boats beautiful. It is not toxic or dangerous, but it can corrode some metals.

At the time of designing a car has to take into account what size is the tank of this additive. Ideally it should last long enough as for the owner does not have to take more until the next review. That is the theory. In practice, it may be necessary to do more than one fill, otherwise the engine will refuse a day to boot.


The oxides of nitrogen, when bombarded with urea (contains ammonia) is broken down into pure nitrogen and water vapor, present in the air pure

We have known recently that Volkswagen, BMW and Daimler agreed from the 90’s to circumvent the rules of the competition, and presumably did so also in matter of technology of selective catalytic reduction (or SCR) using deposits of urea smaller than necessary.

If the urea tank is not large enough, the owner will be forced to take more additive before getting to the review. It is more of a discomfort that a great cost, as it is relatively cheap-if you purchase in the right place less than 30 cents/liter – and lasts thousands of miles for a full tank. A large deposit raises costs for the manufacturer, but it is more comfortable for the owner.

A Mazda CX-7 has a urea tank of 15.5 liters, fill it can come out a little more than 4 euros

According to the inculpatory documents that have been presented to Volkswagen and Daimler, were used for smaller deposits, and that way is to avoid the inconvenience to their customers injecting less urea than necessary. In other words, are contaminated more than necessary to avoid complaints from the users. You could have avoided, yes.


In some models it is necessary urea -yes or yes – to comply with the emission limits, especially outside of laboratories

The exhaust gas of a diesel engine are rich in oxides of nitrogen for a very simple reason: they work with high compression rates and high temperatures, so that the nitrogen (nearly 70% in clean air) is mixed with the oxygen, giving rise to toxic gases and can be dangerous in large urban areas: NO2 and NO3.

Not all manufacturers have resorted to the urea to lower their emissions until the margins legal. In the small cars and the medium has been sufficient to employ catalysts of NOx, which accumulate these gasses and reduce them with heat and compounds that are not consumed. Mazda, for example, has opted to reduce the compression of their engines to emit less NOx, previously employed in the CX-7 urea to meet Euro 5.

But the SCR technique is more effective, and that is why it is used in trucks, buses, SUV’s, vans and sedans large. Now, it should be used the necessary quantity, if it generates more NOx, you must inject more urea, although it is more uncomfortable for the owner of the car. Some reprogramming will involve an increase in the consumption of urea, which does not affect the reliability at all. Is the price to pay for polluting less.


Conversion diesel-LPG. Is initially expensive, but long-term get a savings on fuel and breakdowns, at the same time that you clean a lot of the exhaust. No manufacturer of cars uses this technology, although it could save the Diesel for years

how easy is it to own a diesel is preferred that the urea will last longer, and not have to be aware of if you need to throw an additive in 2,000 or 3,000 kilometres. Before you run out the AdBlue the on-board computers alert you with plenty of time. The engine does not start if the additive has been exhausted, because it would not meet the emission standard for which it is approved. Truck drivers know it very well.

at The end, for having wanted to remain on good terms with the clients and save a little money, it has caused a damage to the environment and the health of the people. More than one manufacturer is going to have to make calls to review to spend the urea that you have to spend, although instead of lasting to 15,000 or 20,000 miles, and the tank lasts only a 3,000 or 5,000. It is difficult to explain this to owners, especially if no one informed them of this before confirming the purchase.

The reality is that a diesel engine can not be clean by itself, you need systems of decontamination that have their drawbacks and faults

The other way is to use injection dual gas+diesel, but this is a hard sell to a particular given the high amortization term. In commercial vehicles the benefits are much more noticeable, because in addition to contaminate less and save up to 30% in diesel oil, and 15% fuel. Then yes we can talk about that it makes economic sense within a more reasonable.