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What is AdBlue

If you’ve bought a new diesel car in the last couple of years, the chances are it’ll need AdBlue at some point.
This guide explains all.....

For many people, AdBlue remains a mystery. So, what is AdBlue? Made up of a mix of urea and deionized water, the fluid is pumped into the exhaust system, helping to reduce nitrous oxide emissions produced by diesel engines. With car manufacturers having to adhere to ever more stringent emissions targets, AdBlue has been a vital addition to diesel cars.

If you cover low mileages, it’s most likely that you won’t have to make any changes to your annual servicing routine to accomodate for AdBlue, as the fluid is topped up as part of a normal service. However, if your mileage is high, be prepared to top up the AdBlue yourself occasionally, as the more you use the car, the quicker the AdBlue will need replacing. Fortunately, topping up your car’s AdBlue is a cheap and straightforward process.

What does AdBlue do and why do we need it?

Car manufacturers are governed by various rules, and increasingly these are driven by environmental concerns. The latest emissions regulations, referred to as Euro 6, came into force in 2016 and represented a particular challenge for the development of diesel engines. Much of this required new ways to minimise nitrogen-oxide emissions.

The technology employed is called selective catalytic reduction, or SCR, which is a technology that involves injecting precise amounts of a liquid into the vehicle exhaust gases.

How does AdBlue work?

To comply with Euro 6 regulations, most new diesel-powered cars built since 2006 use SCR technology to inject tiny quantities of AdBlue into the car’s exhaust gases. When this solution combines with exhaust emissions, it produces harmless nitrogen and oxygen by breaking down the harmful mono-nitrogen oxides in diesel exhaust. This technology has been used in buses and heavy lorries for a long time, so its effectiveness has been proven and its reliability is better than ever.

What is AdBlue made of?

AdBlue is a non-toxic liquid that’s colourless in appearance and is essentially a solution of water and urea – a substance found in urine. However, in AdBlue, the urea is exceptionally pure and is of a higher grade than that used in cosmetics, glue or fertilisers. Similarly, the water is demineralised, which is far cleaner than water from the tap.

When buying AdBlue, you should check it meets the correct specification, so look for the ISO 22241 number on the packaging. This may also appear as ISO-22241-1, ISO-22241-2, ISO-22241-3. This will ensure the AdBlue doesn’t damage your car’s SCR catalyst – a costly repair. Assuming your AdBlue meets these specifications, one brand of AdBlue should be pretty much the same as another, in the same way that diesel fuel is fundamentally the same from one retailer to another.

Does my car use AdBlue?

SCR technology with AdBlue is becoming increasingly commonplace, but isn’t yet fitted to every diesel car. The more recently your car was built, the more likely it is that it’ll use AdBlue to reduce its emissions. If you’re driving a new model launched since 2016, it’s highly likely it’ll use AdBlue; if you’ve bought a new car since 2016 which was on sale before that date, it’s possible it won’t require it.

Many people are unaware the system is installed until a warning message appears on the dashboard announcing the AdBlue tank needs replenishing. As the SCR system has no effect at all on how the car drives, it’s not always obvious whether a car is so-equipped.

If you’re in doubt as to the presence of an SCR system that requires AdBlue, the owner’s handbook for your car will help. You can check it for the location of the AdBlue filler cap – if one isn’t listed, it can be assumed that SCR was never fitted to your model of car, although a call to your local dealer is still recommended.

If it does provide a location for the AdBlue filler, check that location on your car for its presence. Where fitted, it’s commonly beside the fuel filler, but some cars have it concealed by the boot carpet, either on the floor or at either side.

How to refill AdBlue

If you cover more miles than most, you may find you need to refill your AdBlue tank in between services.

Topping up with AdBlue is a simple affair. It’s always a good idea to consult your car’s handbook first, but typically all you need to do is open the AdBlue filler cap, screw on the connecter of the refill bottle, then let the AdBlue drain into the tank. Many larger refill containers require a connecting nozzle, and you may want to buy one of these from a dealer if you’re a high-mileage driver, as larger refills can save you money in the long run.

Some cars require that you use the wheel brace to undo the AdBlue filling cap, and most require that you add a minimum amount (usually around three to five litres) when refilling, in order to remove the warning message from your car’s dashboard.

How to reset the AdBlue warning light

As with your low-fuel warning light, there’s no manual way of resetting it – only topping up to a minimum level will ensure the warning light or the low-AdBlue message disappears.

AdBlue petrol stations

You can buy AdBlue refill bottles from your dealers for about £1.50 a litre, and it’s also sold by shops like Halfords and Euro Car Parts as well as online retailers such as Amazon.

It’s worth topping up as soon as you see a warning message to avoid paying over the odds in an emergency.

What happens if I run out of AdBlue? Driving without AdBlue

While you’ll be reminded in plenty of time to do this by messages on the dashboard, be warned that your car won’t start if you fail to refill the AdBlue tank before it runs completely dry.

How much AdBlue will my car use?

AdBlue consumption varies from vehicle to vehicle, but Volkswagen estimates a Passat will get through about 1.5 litres every 620 miles, for example. Much like fuel, though, the harder and faster you drive, the more AdBlue you’ll use.

Fortunately, because AdBlue is injected into the exhaust gases in such small quantities, you shouldn’t find yourself topping up too often. With most AdBlue tanks holding around 10 litres or more, many drivers will find AdBlue refills taken care of during their car’s annual service.

How long does AdBlue last?

As with any vehicle fluid (including antifreeze and brake fluid), AdBlue will eventually degrade over time. While it’s more than likely that it’ll be replaced before this happens, you should receive a dashboard warning message if this occurs.

While at first it might seem sensible to keep a few extra litres of AdBlue in the boot, this isn’t something we recommend, as any spills or leaks are likely to damage your car’s interior. Do also note that you can’t keep a half-empty container of AdBlue in your garage if you have some left over after topping up, as airborne contaminants can affect the chemical composition of AdBlue.

Is AdBlue harmful?

Although it’s non-toxic, AdBlue is corrosive and can cause irritation to your skin, eyes and lungs, so do wash your hands after filling. Be sure to rinse any spills from the car’s bodywork too, because AdBlue can damage paintwork.

AdBlue cost

If you’ve paid for fixed-price servicing, topping up your car with AdBlue will normally be included in this cost. If you pay for your car services individually, it’s worth checking how much you’ll be charged for replenishing the AdBlue fluid, as it may be cheaper to do this yourself.

Assuming you don’t need to replace your AdBlue there and then, it’s worth shopping around at dealers, petrol stations, car spares stores such as Halfords and Euro Car Parts as well as from online retailers such as Amazon. Typically you’ll pay around £1.40 a litre from a retailer, and around £1.50 from a dealer. Some cars have larger tanks than others, so the price of a full tank will vary.

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