If you drive a modern diesel car, you’ve probably seen the AdBlue warning light pop up on your dashboard at some point. But what exactly is AdBlue, why do diesel cars need it, and what happens if you run out?
What is AdBlue?
AdBlue is a type of diesel exhaust fluid (DEF) that helps reduce harmful emissions from diesel engines. It isn’t a fuel or an additive you pour into your diesel tank. Instead, it’s stored in a separate AdBlue tank and used by your car’s Selective Catalytic Reduction (SCR) system to cut nitrogen oxides (NOx) – gases that contribute to air pollution and smog.
In short: AdBlue makes modern diesels cleaner and road-legal under Euro 6 emissions standards. For businesses running fleet leasing, this is especially important to plan around.
Is AdBlue the same as DEF or AUS 32?
Yes, AdBlue is just a brand name for DEF that meets the ISO 22241 standard. AUS 32 is the technical name. In North America, you’ll hear “DEF” more often, while in Europe, “AdBlue” is the common label.
What is AdBlue made of?
AdBlue is a clear, non-toxic liquid made of 32.5% high-purity urea and 67.5% deionised water. This exact mix, known as AUS 32, is carefully balanced so it works in all weather conditions. To make sure it’s safe for your vehicle, it must meet the ISO 22241 standard.
That means not just any urea solution will do; only certified AdBlue or DEF should go near your car’s system.
How does AdBlue work?
Here’s a quick overview of what AdBlue does:
- When you’re driving, tiny amounts of AdBlue are injected into the hot exhaust gases.
- Inside the SCR catalyst, AdBlue breaks down into ammonia.
The ammonia reacts with the nitrogen oxides (NOx), turning them into harmless nitrogen and water vapour.
It’s worth knowing that this is completely separate from your car’s DPF (diesel particulate filter), which traps soot. Together, the DPF and SCR help diesels meet strict emissions rules.
Which vehicles use AdBlue?
Most Euro 6 diesel vans, cars, and lorries use AdBlue. In the UK, that generally means diesel cars registered after September 2015. If your vehicle has an SCR system, it will have a dedicated AdBlue tank and warning system on the dash.
Looking for a van that’s already built to meet today’s emissions standards? At First Step Vehicle Solutions, we’ve got a wide choice of diesel vans available on flexible van leasing and contract hire deals. Whether you’re after a small van for city runs or a long-term fleet solution, every vehicle comes AdBlue-ready and compliant.
Why getting a high-quality AdBlue matters
Using cheap or contaminated DEF can clog injectors, damage the SCR system, and even void your warranty. Always buy AdBlue in sealed containers from trusted retailers, and make sure it clearly says ISO 22241-compliant. If you’re arranging business van leasing, keeping AdBlue topped up is part of staying compliant and avoiding downtime.
How often will you need to refill AdBlue?
How much AdBlue you’ll use depends on:
- Your vehicle model
- Driving style
- Load and trip length
As a rough guide, most cars go 3,000 to 6,000 miles between top-ups. Many dashboards show an AdBlue range, so you’ll know how far you can go before the tank runs dry.
Top tip: When you’re arranging new van leasing, check the AdBlue tank size – it’ll tell you how often you’ll be refilling.
How do I refill AdBlue?
Refilling your AdBlue is straightforward:
- Find the filler: It might be next to the fuel cap, under the bonnet, or in the boot.
- Use the right container: Most bottles come with a nozzle to avoid spills.
- Don’t mix up tanks: Accidentally putting AdBlue into your diesel tank (or vice versa) can cause costly damage.
- If you do spill some, rinse it with water – it can crystallise if left to dry.
What happens if you run out of AdBlue?
Your car will give you plenty of warnings as the AdBlue level gets low. Ignore them, and eventually the system will put the car into limp mode or prevent it from restarting altogether. That’s because driving without AdBlue means your car can’t meet emissions standards – and manufacturers are legally required to stop you.
AdBlue storage, shelf life, and freezing
- Shelf life: AdBlue lasts about a year if stored sealed, cool, and out of sunlight.
- Freezing: It freezes at around −11°C, but don’t worry – vehicles often have heaters in the AdBlue tank to thaw it automatically.
- Do not dilute: Adding water ruins the exact mix needed for the SCR catalyst.
How much does AdBlue cost and where can I buy it?
AdBlue is widely available: at supermarkets, petrol stations, motor factors, and online. You can buy small 5–10 litre containers for top-ups or bigger drums if you cover high mileage. Prices for bulk orders are generally cheaper, often coming in lower than £1 per litre. Running long-term van hire? Keep AdBlue in mind for budget planning.
Common AdBlue mistakes and myths
- Never pour it into the diesel tank – this can write off your fuel system.
- Don’t use water or DIY substitutes – they won’t work and could wreck the SCR.
- Don’t ignore crystals – wipe away dried spills before they corrode surfaces.
- Avoid “AdBlue emulators” – illegal devices that trick the car into thinking it has AdBlue. Using one can land you with fines and invalidate your insurance.
What is AdBlue? Final thoughts
AdBlue isn’t something you think about every day, until the warning light pops up. But it’s a simple fix. Just like topping up screenwash, it’s part of keeping your diesel running clean, efficient, and road-legal under strict emissions rules.
If you’d rather not stress about maintenance, First Step Vehicle Solutions has you covered. Our Euro 6 diesel vans come fully compliant and ready for the road, with flexible van leasing and business hire options to suit every need.