Diesel Warning Lights Explained: AdBlue and DPF
If you drive — or are thinking about leasing — a diesel car, you’ll probably come across AdBlue© and DPF systems. These are designed to reduce emissions, but they can also cause confusion when warning lights appear on your dashboard.
This guide explains what they are, what the warning lights mean, and what to do if something goes wrong.
Key takeaways
AdBlue© reduces emissions in modern diesel cars
DPF filters out soot from the exhaust
Both systems are essential for Euro 6 diesel vehicles
Warning lights should never be ignored
Most issues are easy to resolve if caught early
What is AdBlue© Solution for Diesel Engines?
AdBlue© is a registered trademark for a solution that reduces emissions from the exhausts of UK diesel vehicles to comply with Euro 6 emissions standards
What is AdBlue© and how does it work?
AdBlue© is a non-toxic fluid used in modern diesel cars to reduce harmful emissions. It’s made from purified water and urea. The system works by injecting AdBlue© into the exhaust, where it helps break down harmful gases (NOx) into nitrogen and water vapour.
Originally just seen in Euro 6 compliant commercial vehicles, AdBlue© injection systems are now becoming a feature of all new modern diesel vehicles to hit emissions targets.
Does my vehicle need AdBlue©?
Most modern diesel cars (Euro 6) use AdBlue©.
You can usually tell by:
An AdBlue© filler cap (often near the fuel cap or under the bonnet)
A dashboard warning light
If you’re unsure, check your handbook or ask your leasing provider.
When does AdBlue© need to be topped up?
A full top up of AdBlue© should last between 3000 and 20,000 miles depending on the manufacturer and sometimes doesn’t need topping up until your next service.
All vehicles also have a warning system on the dash which will let you know when the AdBlue© is running low or needs a top-up. This is normal, so don't panic. Do not ignore the warning light as some vehicles will refuse to start if they run out of AdBlue©, and you might face recovery or repair costs.
What you should do
Top up AdBlue© as soon as possible
Follow your vehicle’s guidance on quantity
Avoid letting it run completely empty
Handle AdBlue© with care. AdBlue© damages surfaces such as paintwork, clothing and carpets. Use gloves and be careful not to get in your eyes.
Don’t be tempted to keep AdBlue© in your boot. If spilled, AdBlue© can damage carpets or paintwork.
If the wrong liquid is poured into the tank do not start the engine and call you funder immediately.
Remember, it's your responsibility to keep the AdBlue© levels filled and not to ignore the warning light.
Diesel Particulate Filter (DPF) for Diesel Engines
What is a DPF?
DPF stands for Diesel Particulate Filter. It captures soot from your exhaust to reduce emissions. Over time, the filter fills up and needs to clean itself — this is called regeneration.
Most new diesel vehicles are fitted with a DPF, lowering your vehicle's emissions and meeting European emissions legislation.
How does DPF regeneration work?
The car traps bits of soot from the exhaust in the filter. Periodically the car will burn off the soot at high temperatures. This usually happens when:
You drive at consistent speeds
The engine gets hot enough
What to do if a DPF warning light comes on?
This is one of the most common diesel issues. It lets you know that the DPF needs assistance in regeneration. It will generally mean that:
The filter is blocked and not regenerating properly
This is usually caused by short, low-speed journeys
How to fix it
In many cases, you can clear it by:
Driving for 15–20 minutes
At a steady speed (around 50mph if safe)
Keeping revs higher than usual (around 2,000–2,500 rpm)
This allows the system to complete regeneration. You manual will contain specific guidance for you to follow if traffic or speed limits restrict you from assisting regeneration.
However, if after trying this:
The warning light stays on
Or multiple warning lights appear
Contact a garage or authorised repairer immediately. Ignoring the warning could lead to a reduction in power and mechanical failure that isn't covered by warranty.
How to avoid common diesel issues
You can prevent most problems with a few simple habits:
Take the car on a longer run occasionally
Respond to warning lights early
Keep AdBlue© topped up
Follow the recommended service schedule
Diesel still suits some drivers very well. It's often a good choice if you drive long distances regularly, spend time on motorways, or need strong fuel efficiency at higher speeds.
How leasing helps
Leasing a diesel car can reduce some of the risks because:
You’re driving a newer, more reliable vehicle
You benefit from manufacturer warranty cover
You can add a maintenance package to cover servicing
At LeaseCar, we offer regular deals on new diesel vehicles, or simply call us on 0344 745 1818 to discuss a lease that's right for your needs.