AdBlue is a fairly recent introduction in diesel emission technology for cars and has led to some problems for drivers unfamiliar with the technology and its maintenance.

The product has been in use in heavy commercials for quite some time now but has only been used in cars in the last few years. It is also known as DEF (Diesel Exhaust Fluid).

So what is AdBlue ?

AdBlue is an aqueous urea solution made with 32.5% urea and 67.5% deionized water.

The urea solution is clear, non-toxic and safe to handle. However, it can corrode some metals and so must be stored and transported carefully.

DEF is stored in a tank on board the vehicle, and injected into the exhaust stream by a metering system

It is sold in filling stations in various sized containers but is also widely available at pumps in larger stations that trucks use.

What does it do?

It is injected into the exhaust system and then vaporized into a gas which turns harmful particulates called nitrogen oxides into water and nitrogen which are then expelled into the atmosphere. This leads to a big reduction in harmful emissions.

Where is it stored in the car?

AdBlue is stored in a small tank on the vehicle and can be recognized by a small blue lid about half the size of the fuel filler cap. The location varies from car to car but more information can be found in the owner’s manual.

Does it need maintenance?

Other than topping up the tank occasionally it is maintenance free. A low level warning will display on the dash to let you know when it needs more fluid. Do not ignore this warning as it will eventually prevent the vehicle from starting.

So what’s the problem with AdBlue ?

Well first the name….it’s neither an additive nor is it blue.

Some people have mistakenly put AdBlue into the fuel tank of their vehicle and driven the vehicle. The vehicle will break down shortly after and it will then be necessary to drain and flush the complete system. The potential for further damage is also possible.

Unlike petrol or diesel, AdBlue is not a hydrocarbon based product and has a higher specific gravity. In other words it will separate from the fuel and sink to the bottom of the fuel tank. Here it will be sucked up by the fuel pump and fed into the injection system. When this happens the engine will stop.

At this stage the tank, the fuel lines, the filtration system and have to be cleaned and maybe even replaced.

AdBlue is a registered trade name of VDA (Germany)