HAT IS ADBLUE?
How does AdBlue work – and does my car have it?
AdBlue reduces harmful emissions – but if you run out, your car won’t start
Many new diesel cars use a fluid called AdBlue. If your car uses AdBlue, you'll probably need to top it up at least once between services.
Find out what it does, how it works and why it’s important to keep an eye on dashboard warnings - particularly if you’re a high mileage motorist.
Adblue filler cap
What is AdBlue?
AdBlue is an exhaust fluid, not a fuel additive. It's stored in a separate reservoir and is topped up via a (usually) blue filler cap located either next to your fuel filler, in the boot or under the bonnet.
It's a trade name registered by the German car manufacturers association, but is the most recognised form of Diesel Exhaust Fluid (DEF).
What is AdBlue made of?
AdBlue is a colourless, non-toxic mixture of urea and de-ionised water. It’s not actually blue at all.
Lots of people think AdBlue is made of pig urine – it’s not. The urea used in AdBlue is a high purity man-made solution – pig urine wouldn’t be pure or sterile enough for a commercial product.
How does AdBlue work?
Tiny amounts of AdBlue are injected into the flow of exhaust gases. At high temperatures AdBlue turns to ammonia and carbon dioxide.
Inside the SCR (Selective Catalytic Reduction) catalyst, harmful nitrogen oxide in the exhaust reacts with the ammonia and is transformed to harmless nitrogen and water.
Similar technology has been used effectively for years in buses and heavy lorries.
Need breakdown cover? Read our guide about how it works:
A guide to breakdown cover
What happens if I run out of AdBlue?
If you run out of AdBlue while you’re driving, then the engine’s power and performance will be reduced to limit its emissions. Once you’ve stopped, you won’t be able to restart the engine if the AdBlue tank’s empty.
The car will give you plenty of warning that the AdBlue tank’s running low. You'll usually see a text warning on the dashboard at around 1500 miles to go followed by an amber warning light.
Which cars can use AdBlue?
Not all car manufacturers use AdBlue technology. But chances are if you’ve got a diesel from Jaguar, Land Rover or any French or German manufacturer, and it was registered new after September 2015, it’ll use AdBlue.
Does my car use AdBlue?
Some older cars or vehicles from other manufacturers use AdBlue too. So if you’re not sure if your car uses it, you can check:
The vehicle handbook.
See if there’s an AdBlue filler cap either next to the fuel filler, in the boot or under the bonnet.
If the model name contains ‘Blue’ or ‘SCR’.
If you’re still not sure, ask a dealer.
Where can I buy AdBlue?
AdBlue’s sold by petrol stations, garages, motor accessory shops, online retailers and even some supermarkets. If you’re in any doubt that you’re buying the right stuff, contact your dealer.
It’s widely available in 1.5, 5 and 10 litre containers. The smaller packs have a specially-designed neck that lets you top up the tank without risk of spillage even if you don't have a funnel.
With easy-fill bottles available, it's a good idea to carry a small container of AdBlue so you’re ready to top-up when necessary.
How long does AdBlue last?
The rate at which you use AdBlue depends on your engine and how economically you drive.
Typical consumption is around a litre of AdBlue every 600 miles.
But it could be as high as a litre every 350 miles.
Tank size varies too, so you could need to refill somewhere between 3,000 and 12,000 miles depending on the car and your driving style.
This means that most drivers will have to top-up their AdBlue reservoir at least once between normal service visits to the dealer.
Is it safe to drive with the AdBlue warning light on?
It’s not a major safety issue, but if you don’t top up, you’ll eventually run out of AdBlue and you won’t be able to start the car.
When the warning light first comes on you’ll have plenty of time to refill – so don’t panic. Just make sure you don’t put off topping up.
How to reset the AdBlue warning light
There’s no manual way of resetting your AdBlue warning light – the only thing you can do is top up. Once you’ve refilled to the minimum level, the warning light will disappear.
Where is the AdBlue tank?
Step-by-step explanation:
