The “Secret” Fluid: Why your Peugeot or Citroën needs more than just AdBlue.
If you drive a diesel Peugeot, Citroën, or certain Ford and Volvo models, you might have encountered a warning message that sounds like a science experiment: “Particle Filter Additive Level Low.”
Many drivers head straight for the AdBlue pump, only to find the warning remains. That’s because your car uses a secondary, specialized liquid known as Eolys fluid (or PAT fluid).
At Carbon Clean Co, we are one of the few mobile specialists in the East Midlands equipped to refill and reset these systems. Here is everything you need to know about this “secret” engine fluid.
1. What is Eolys Fluid?
Unlike AdBlue, which is sprayed into the exhaust to reduce NOx gases, Eolys is a fuel-borne catalyst. It lives in a dedicated tank or a flexible “pouch” near your fuel tank. Every time you fill up with diesel, a tiny, precise amount of Eolys is injected directly into your fuel tank.
2. What Does It Actually Do?
The job of Eolys is to help your Diesel Particulate Filter (DPF) stay clean. Normally, soot burns off at roughly 600°C, but exhaust gases rarely get that hot during normal driving. Eolys fluid lowers the combustion temperature of the soot to around 450°C. This allows your car to perform a DPF regeneration much more easily, even during slower, urban driving.
3. Why Can’t I Just Refill It Myself?
While you can buy AdBlue at any petrol station, Eolys is a different beast:
- Highly Toxic: It is a hazardous chemical that requires specific PPE and handling.
- Complex Access: The tank or bag is often hidden behind wheel arch liners or underbody shields.
- The “Brain” Reset: Even after refilling the fluid, the car’s ECU won’t know it’s full. You need professional diagnostic software (like the tools we carry at Carbon Clean Co) to tell the car the reservoir is replenished and to clear the fault codes.
4. How Long Does It Last?
Typically, a full tank or pouch of Eolys lasts between 60,000 and 80,000 miles, depending on your driving style and how often you refuel. If the additive runs out, your DPF will stop regenerating, leading to a blocked filter within a few hundred miles.
The Specialist Alternative to Main Dealers
Main dealers often charge eye-watering prices for PAT fluid refills, sometimes insisting on replacing the entire housing instead of just the fluid or pouch.
At Carbon Clean Co, we offer a mobile Eolys refill service. We come to you, use the correct grade of fluid for your specific year and model, and perform the digital reset on-site.
Is your dashboard asking for “Particle Filter Additive”? Don’t ignore it. Call Carbon Clean Co today on 01509 434989 for a mobile refill across the East Midlands.