Can you drive without AdBlue®?

Wondering if it’s possible to drive without AdBlue®? If you drive a diesel vehicle equipped with SCR technology, AdBlue® (also known as diesel exhaust fluid or DEF) is one of the elements required for the engine to function. What can you expect when the AdBlue® tank is empty? Is it possible to drive without refuelling? All the answers in this article.

Can you drive without AdBlue®? What are the risks?

Driving without AdBlue® or diesel exhaust fluid (DEF) in your vehicle’s dedicated tank is theoretically not possible. In fact, if your AdBlue® tank is empty, your diesel vehicle’s engine will simply stop and won’t be able to restart until you top it up. AdBlue® is an integral part of the operation of vehicles fitted with SCR catalysts.

To better understand the benefits of this liquid, it may be useful to recall what AdBlue® is and what it is used for. AdBlue® (or DEF) is a solution composed of 67.5% demineralised water and 32.5% high-purity urea. It is designed to drastically reduce polluting emissions from diesel engines.

How is AdBlue® used? When the engine is started, AdBlue® is introduced into the exhaust system, upstream of the SCR catalyst. The ambient heat in the pipe causes the urea in the AdBlue® to transform into gaseous ammonia. On entering the catalyst, the nitrogen oxides and ammonia mix to produce nitrogen and water vapour, which are harmless to humans and the environment. These two substances are then released into the environment.

As the SCR system is designed to operate only in the presence of AdBlue®, the absence of this liquid normally makes it impossible to ignite the engine.

Cheating the system to drive without AdBlue®?

As mentioned above, it is theoretically impossible to start a car fitted with an SCR system if the AdBlue® tank is empty. To circumvent SCR technology, some drivers manage to simulate the presence of AdBlue® in the tank by filling it with water. Be aware that this method is dangerous, and could cause serious damage to your vehicle. As the saying goes, prevention is better than cure! If you’re about to run out of AdBlue or the AdBlue® warning light has just come on, think ahead: get a can of AdBlue® quickly so you can top it up yourself rather than running out.

Now let’s talk about a solution that’s totally illegal, but which makes some ethically dubious companies happy. It involves the installation of electronic devices designed to neutralise or deactivate the AdBlue® system. When a car is fitted with this type of device, it is theoretically capable of driving without AdBlue®. Be aware that the use of such a device is prohibited by law and will expose you to penalties if you are subject to an inspection.

Running out of AdBlue®: how do I get back on the road?

Your AdBlue® tank is empty and your engine refuses to start? In most cases, all you need to do is get a can of AdBlue® (10 litres, for peace of mind for a while) and refill the dedicated tank. To do this, you can either order a canister on the internet (if you don’t need it urgently), or collect a canister from a service station (make sure they have some in stock before you go).

Note that sometimes, despite topping up the tank, the vehicle is still impossible to start. In this case, don’t hesitate to contact your car dealer.

We can’t stress this enough: don’t wait until you run out of AdBlue® to fill up. You risk not being able to start. As soon as you see the AdBlue® or Urea indicator or a warning message, fill your tank quickly.