What is AdBlue?

20 March 2025

An essential automotive fluid for some diesel vehicle owners.

AdBlue is the brand name of an automotive fluid known as diesel exhaust fluid.

AdBlue diesel exhaust fluid is used in many trucks and in some diesel-powered light vehicles to reduce nitrogen oxides emitted from the tailpipe.

Nitrogen oxides are a pollutant emitted by both petrol and diesel engines however diesel engines produce a higher amount of these harmful gases.

Nitrogen oxides can cause a variety of health issues, including irritation and inflammation of the respiratory system, exacerbation of asthma, and reduced immunity to respiratory infections.

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AdBlue contains urea, which is a common ingredient in fertiliser, and purified water. When mixed with a diesel engine’s exhaust, it produces a less polluting mixture of nitrogen, water, and carbon dioxide.

Diesel vehicles that require AdBlue have a separate tank that holds the fluid. The filler point for the tank is usually located next to the fuel filler.

AdBlue isn’t mixed with fuel at any point. It is injected into the vehicle’s exhaust system, where it turns the nitrogen oxide into nitrogen and water.

It should never be added directly to a diesel vehicle’s fuel tank; if it is, do not drive the vehicle or even turn on the ignition. The fuel system will need to be fully drained and checked by a qualified technician.

Where can you get AdBlue?

Some service stations have an AdBlue bowser where you can top up your DEF tank while getting fuel, otherwise it’s available to buy in bottles from service stations and auto stores. It’s a good idea to have a bottle with you on longer trips.

If you are filling up at a service station, check the fuel bowser labelling carefully to ensure it is AdBlue and that you’re pumping it into the correct tank.

If you’re buying AdBlue in bottles from an automotive retailer, a 10-litre bottle costs about $60. Smaller bottle sizes are also available. Filling up at a service station will generally cost less per litre.

How much you use will depend on your fuel consumption. Especially if you’re going to be towing on a longer trip, ensure your AdBlue tank is full.

Tank sizes vary depending on the vehicle, but the average tank holds around 15 to 20 litres. You’ll need approximately 10 to 15 litres for every 10,000km of driving.

Do I need to use AdBlue?

If your diesel vehicle has a tank for AdBlue, then you will need to use it. Without it, your vehicle may not start, or ‘limp mode’ may be activated, causing the vehicle to lose power and some functions to be switched off.

When AdBlue is low, you’ll see a dashboard warning light. Some vehicles also have a gauge which shows the level in the tank.

Many diesel vehicles from Europe need AdBlue due to more stringent vehicle emissions regulations in EU countries, and it is becoming more common in other diesel vehicles. New Toyota Prados sold in Australia, for example, now have a DEF tank.

While not classified as a toxic substance, it is corrosive, so ensure you wipe up any residue or spills and wear gloves if filling from a bottle directly into the tank.

If storing it at home, be aware that AdBlue has a shelf life of approximately 12 months.

Despite the brand name AdBlue, DEF is actually colourless.