What is AdBlue?

If you’ve bought a new diesel car over the past five years or so chances are it uses AdBlue to help make its exhaust emissions cleaner. In fact, if your car uses AdBlue, it won’t be able to run without it.

Which begs the question – what is AdBlue, how does it work, where can you buy it and how do you refill it? For the answers to these questions, and more, read on for carwow’s guide to everything you need to know about AdBlue.

AdBlue and diesel emissions

Diesel engines were originally supposed to be one of the solutions to climate change because they produce far less CO2 emissions (harmful greenhouse gases) than an equivalent petrol engine. The government even legislated lower company and road tax charges to encourage you to buy a diesel.

Much like governments, though, consensus changes and diesel isn’t the silver bullet we once thought it was because, although it reduces CO2s, it also produces more sooty particles and N02 emissions than an equivalent petrol engine.

AdBlue is the solution to the first of those two issues and became a requirement with the introduction of tough new Euro 6 legislation in September 2015. Injected into your car’s exhaust, AdBlue is fed into the exhaust and reacts with the nitrogen oxide gas in the exhaust gases, breaking down into harmless nitrogen and oxygen. How effective is it? Well, actually, very. In fact, in 2017 a study conducted by the University of Leeds found that a Volkswagen Polo fitted with a 1.4-litre diesel engine produced as much toxic nitrogen dioxide gas as 13-litre diesel lorry that did have an AdBlue system fitted.

What does AdBlue do?

Without AdBlue, a very large amount of the newest diesel cars currently on sale would produce too much nitrous oxide to be allowed on the road under Euro 6 rules. It is a non-toxic liquid – made mostly of water and urea (yes, the stuff in pee) – that is used as a part of selective catalytic reduction (SCR). SCR breaks down the nitrous oxide produced by diesel engines. By squirting small splashes of the liquid into the exhaust, it turns the waste into harmless water and nitrogen. Hey, presto! – your car is suddenly a whole lot kinder to the environment.

Do I need AdBlue?

If your car requires AdBlue – i.e., it’s a diesel that conforms to Euro 6 legislation – and you let it run out, the engine won’t start. Luckily, almost all cars that need it have a display or a warning light that will let you know how much is left and when you need to give it a top-up.

When do I refill AdBlue?

How long your AdBlue lasts depends on a lot of factors, such as the size of your car’s tank, your own personal driving style and your car’s fuel consumption. However, to give a rough estimate, the AA reckons you should burn through around a litre of the stuff for every 600 miles you drive.

When you’re refilling your AdBlue, you can’t ‘splash and dash’ the way you can with fuel. If you refill only a small amount, it won’t register when you check the measuring gauge inside your car. Also, if you buy a bottle of AdBlue so that you can refill your car’s levels yourself, you have to use all of it; a half-empty bottle won’t keep for later.

How do I refill AdBlue?

Refilling AdBlue is like refilling your petrol tank. In the vast majority of cases, you’ll find the refill pipe beneath the fuel filler cap, next to your diesel filler. Just pour the liquid in (or don’t, if you’re getting a mechanic or manufacturer to do it for you) and you’re all set!

Where to buy AdBlue (AdBlue pumps):

Bottles of AdBlue can be found in most petrol stations – especially those belonging to chains like Shell or Texaco – and motoring shops, such as Halfords.

It’s also possible to refill your AdBlue from a pump at petrol stations, similar to fuel. However, stations with pumps are rare in the UK.

If your car is being serviced and your AdBlue levels are running low, the garage can top up your levels for you. The same can be true if you buy directly from your car’s manufacturer, with the bonus that some of them free limitless top-ups.

When you buy your AdBlue, check for a code on its label beginning with ‘ISO-22241’. This means that the fluid in question won’t damage your car’s SCR system, which can prove very expensive to repair or replace. Picking the wrong type can also void your car’s warranty.

AdBlue prices:

The cost of AdBlue can vary. However, in most cases, you can find a five-litre bottle on store or petrol station shelves for around £5.

Topping up at the pumps or during a service can prove much more expensive, so you’d best stick to refilling your car yourself whenever you can.

Popular manufacturers with AdBlue:

Audi AdBlue:

Your Audi will let you know when it is 1,500 miles away from running out of AdBlue by flashing a warning message on its digital screen. An Audi main dealer service centre can refill your tank at a fixed rate of £1.50 per litre.

BMW AdBlue:

BMW claims that its cars can last an average of 15,000km (9,321 miles) before needing to be refilled. If your range drops below 1,600km (994 miles), a warning will automatically come up on your display, counting down the miles until your car’s tank needs refilling.

Mercedes AdBlue:

If you buy a bottle of the blue stuff from an official Mercedes service centre, they will give you limitless refills for no extra charge. A warning message will flash up on the car’s dashboard when you’re hitting your reserve.

Volkswagen AdBlue:

Volkswagen gives you a 1,500-mile warning that your fluid’s running low with a countdown until the tank’s empty.

The company is also one of the few to quote what you can expect from a tank of AdBlue across its model range. So, a Volkswagen Passat with a 13-litre tank should be good for up to 6,500 miles between top-ups. The biggest car the brand sells, the Volkswagen Touareg SUV, has a 19.5-litre tank, which will last up to 7,000 miles between top-ups.

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