How to add Diesel Exhaust Fluid (DEF) to a 2012 – 2015 Passat TDI


Diesel exhaust fluid (DEF) is composed of urea and de-ionised water and is injected into the exhaust gasses of many modern diesel engines.  DEF significantly reduces the amount of exhaust gas emissions and pollution by converting harmful nitrogen oxides into harmless nitrogen and steam.

Most vehicles equipped with DEF will have a dedicated tank that requires to be refilled at normal service intervals. The size of the tank is usually designed so that you should not have to refill the fluid in between services, however individual vehicle’s consumption may be higher depending on operating conditions. The vehicle will not operate unless there is sufficient fluid in the vehicle’s tank.

The following is a guide for adding Diesel exhaust fluid to a 2012 – 2015 Passat TDI (additional years and models may also apply)

Step 1:

Open the trunk and locate the cover for the tank on the passenger side of the vehicle.


Step 2:

Remove the plastic cover by gently pushing in and up from the bottom.



Step 3:

Unscrew the cap by twisting it counter-clockwise


Step 4:

Grab your bottle of Diesel exhaust fluid and carefully pour it into the tank. It is important that you check the capacity for your specific vehicle in the owners manual to avoid overfilling.


I chose to use a bottle from a local Volkswagen dealer which comes with an attachment on the end that screws into the tank so no fluid gets spilled. You can also purchase bulk fluid at most auto part stores, but you will need to use a funnel and pour slowly so that it doesn’t splash all over the place. In this case, I used about 3 bottles, or about 1.5 gallons of fluid.

Step 5:

Replace the cap and re-install the plastic cover.



That’s it! You’re all done.


NOTE: Diesel exhaust fluid is very easy to use and is a harmless substance. It is non-flammable and non-explosive. If you ever spill AdBlue on your hands, simply wash them thoroughly with water.

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