April 26, 2019

AdBlue Confusion

Drivers Are Still Making AdBlue Mistakes Five Years On

AdBlue technology was first introduced in passenger cars in 2014 with the advent of the Euro 6 emissions standard, and it has been widely used in HGVs for around a decade longer. But, despite this history and the fact that the majority of modern diesel cars use AdBlue, there still appears to be a significant amount of ignorance about what it is and how it should be used.

The most recent data collected on AdBlue-related breakdowns was published by the AA in June 2018. This showed that they had dealt with over 23k AdBlue related breakdowns in the previous year, almost double the number of the year before that. As the custodians of over 15k vehicles ourselves, we’re also coming across a large number of AdBlue mishaps. So much so, in fact, that we’ve put together a guide on the use of AdBlue for drivers.

What is AdBlue?

It is a little complex, but basically AdBlue is a chemical compound (urea and de-ionised water), that’s injected into the exhaust system of modern diesel engines to dramatically reduce the emissions of harmful nitrogen oxides (NOx). As Euro emissions standards have tightened, the amount of NOx that engines are legally allowed to emit has reduced, and manufacturers have increasingly turned to AdBlue technology to ensure that their cars are compliant.


AdBlue mistakes and problems

The main problem that we’ve encountered is cars running out of AdBlue. Every car requiring the compound will also have a system for warning the driver that it’s running low on the fluid. Generally, this will include a gauge of some sort that shows how full the tank is, plus an increasingly insistent set of warning lights and sounds as levels become very low.

You would imagine that few drivers would ignore these warnings to the point that the AdBlue tank is entirely empty, but there do appear to be a number of factors that make this quite common.

The first is driving an unfamiliar car. If you’re used to driving a regular petrol car, or an alternative fuel vehicle, it’s quite possible that you won’t know what the warnings mean, or even what AdBlue is. With modern cars providing so much information, and so many warnings about their condition and their surroundings, it’s easy to see why these warnings might not register as critical. With increases in the use of short-term rental, medium-term ‘mini-leases’ and car-sharing services this issue is exacerbated.

The second factor appears to be that drivers do not recognise how critical the AdBlue systems are to the running of the car. Completely running out won’t damage the vehicle, but it will cause it to switch to an alternative engine mapping in an attempt to stay within the allowed level of emissions. This will mean a notable reduction in performance until the reservoir is topped up.

Even more problematic is that if you turn off the engine while the AdBlue tank is empty, the car will refuse to start until it is replenished; some cars may even require a visit to the dealer to be reset if this happens. From this it’s easy to see why so many drivers get stranded.

But it can be much worse …

The worst AdBlue mistakes to make are those regarding accidental mixing with the fuel.

If you somehow get diesel into the AdBlue tank and start the engine, the fuel will be injected into the exhaust catalyst system and is likely to cause significant, costly damage. If you do think that your AdBlue has been contaminated in this way, you should not attempt to drive the car and should arrange for a dealer to drain and flush the AdBlue tank.

Getting AdBlue into the diesel tank can have even more calamitous results. As above, if you think that cross-contamination has happened, don’t start the engine and get the diesel tank completely cleaned by a dealer. If you do start the engine it’s unlikely to run for very long. AdBlue is less dense than diesel, so will float on the surface, be picked up by the fuel pump and fed through the injectors. As these components use the diesel to lubricate themselves, this can mean catastrophic damage and require the replacement of the entire fuel system, potentially even writing-off the engine itself.

While obviously an embarrassing mistake, it’s quite easy to see why drivers might assume that AdBlue is a fuel ‘additive’ and, therefore, add it to the diesel tank. It’s important to remember that AdBlue never enters the engine and is only used to treat the exhaust gases leaving it.

AdBlue mistakes are easy to avoid

So, if you happen to be driving a new or unfamiliar diesel car, there are a few simple things to check to prevent any AdBlue mistakes.

First of all, check what the AdBlue levels are before you drive the car; if it is already showing warning lights, or you’re at all concerned about whether there’s enough for your journey, go to your nearest service station and top it up. It’s readily available, usually in five litre containers with nozzles that will fit the filler opening to avoid spills.

In order to be able to do this, you’ll need to know where the AdBlue filler is. In most cars this is a small additional filler next to the diesel and will have its own (often blue) filler cap. A great piece of advice is to keep the diesel cap in place when filling with AdBlue and vice versa, just to ensure there can be no contamination. In some cars, the filler might be found in the engine bay or in the luggage compartment, so check the handbook to make sure you know where to locate it.

Vehicle rental companies would do well to make sure that drivers are informed about AdBlue when they collect the vehicle. Making this information part of the pre-handover vehicle check by staff and driver would preempt any issues.

Obviously, the best advice is to maintain an awareness of the AdBlue levels in the car and top it up well before it could become an issue. Modern diesel-powered cars are cleaner than ever and provide a great solution for many drivers, particularly those covering long distances. AdBlue plays a key role in their performance and, by being aware of how it works, drivers should never find it problematic.

For more info on AdBlue and how to use it, see our guide here.