DPF issues and how to prevent them

Cars with Diesel Particulate Filters (DPFs) suffer problems due to the way these filters trap and burn off soot particles from diesel exhaust. Issues arise when the DPF fails to regenerate properly, leading to clogging and expensive repairs.

For those doing regular long motorway drives or perhaps have the need to tow, a diesel car can still be a good option in 2025. But the impressive co2 figures, mpg, and 0-60 performance that we see on many modern diesel cars comes at a cost for some - and that cost just might be reliability.

Diesel Particulate Filters (DPFs) are present in many modern diesel engines and are a common cause of engine damage and failure.

Here are the main reasons why DPFs cause problems

1. Short Journeys & Stop-Start Driving

• DPFs require high temperatures (≥600°C) to burn off soot during regeneration.

• Short trips and city driving don’t allow proper regeneration, leading to soot buildup and clogging.

• This triggers warning lights and can force limp mode, restricting engine power.

2. Faulty or Incomplete Regeneration

• Passive Regeneration happens automatically at highway speeds but fails in low-speed driving.

• Active Regeneration injects extra fuel to burn off soot, but if interrupted (e.g., stopping mid-cycle), it increases fuel dilution, damaging engine oil.

• Forced Regeneration by a mechanic is needed when the DPF is too clogged.

3. EGR (Exhaust Gas Recirculation) & Oil Contamination

• A faulty EGR valve increases soot production, clogging the DPF faster.

• Regeneration sometimes dilutes engine oil with diesel, causing wear and potential engine damage.

4. Poor Fuel Quality & Driving Habits

• Low-quality diesel produces more soot, clogging the DPF quicker.

• Driving at low RPMs constantly (e.g., below 2,000 RPM) doesn’t allow the exhaust to get hot enough for regeneration.

5. Sensor & Software Issues

• DPF pressure and temperature sensors can fail, triggering false warnings or preventing regeneration.

• Some cars have poorly designed regeneration logic, causing excessive fuel use and DPF issues.

Using premium fuel can help your diesel engine to produce less soot and therefore improve the performance of the DPF over a longer time period.

Engines with known issues

Many diesel engines suffer from DPF (Diesel Particulate Filter) issues, but some are particularly notorious due to poor regeneration, excessive soot buildup, or bad design. Here are three of the worst offenders:

1.6 HDi / TDCi (Peugeot, Citroën, Ford, Volvo, Mini)

Common Models:

• Peugeot 207, 308, 508, Partner

• Citroën C3, C4, Berlingo

• Ford Focus, Fiesta, C-Max

• Volvo S40, V50, C30

• Mini Cooper D

Why It’s Bad:
❌ Eolys Fluid Dependency – This engine uses a special Eolys additive to aid DPF regeneration, but when the fluid runs low, the DPF stops regenerating properly, leading to severe clogging.
❌ Weak Turbo & Injectors – Leaky injectors and turbo problems lead to excessive soot buildup, choking the DPF.
❌ Frequent Sensor Failures – The DPF pressure sensor often fails, triggering limp mode.

Verdict:
🚨 One of the worst small diesel engines for DPF problems! If you only do short trips, avoid this engine entirely.

2.0 TDI (VW, Audi, Seat, Skoda - EA189 & EA288)

Common Models:

• Volkswagen Golf, Passat, Tiguan, Transporter

• Audi A3, A4, A6

• Seat Leon, Ibiza

• Skoda Octavia, Superb

Why It’s Bad:
❌ Regeneration Issues – The engine struggles to complete DPF regeneration, especially with stop-start driving.
❌ Oil Dilution – Excess fuel injected for regeneration leaks into the oil, reducing lubrication and damaging the engine.
❌ EGR & Turbo Problems – A blocked EGR valve increases soot, while failing turbos add oil contamination, both leading to DPF failure.

Verdict:
🚨 The EA189 (pre-2015 Dieselgate engines) were some of the worst for DPF issues, but even the newer EA288 engines (post-2015) still suffer from clogging.

1.3 CDTi / MultiJet (Fiat, Opel, Vauxhall, Suzuki)

Common Models:

• Fiat 500, Panda, Doblo, Punto

• Opel/Vauxhall Corsa, Astra, Combo

• Suzuki Swift, SX4

Why It’s Bad:
❌ Small Engine, Big DPF Issues – The small 1.3L engine doesn’t generate enough heat for effective DPF regeneration.
❌ Fails in City Driving – This engine was commonly used in small city cars, but stop-start driving ruins the DPF.
❌ Expensive Fixes – Forced regeneration often doesn’t work, leading to costly DPF replacements.

Verdict:
🚨 Horrible choice for city driving! The DPF system is completely unsuitable for short journeys.

Honorable Mentions (Also Bad)

🔹 1.6 TDI (VW, Audi, Seat, Skoda) – Same issues as the 2.0 TDI, but worse in city driving.
🔹 2.2 Skyactiv-D (Mazda) – Regeneration problems and high oil dilution rates.
🔹 2.0 Ingenium Diesel (Jaguar Land Rover) – Prone to premature DPF clogging, leading to frequent limp mode.

Final Advice: How to Avoid DPF Problems

✅ Do regular motorway runs (20+ mins at 2,000+ RPM) to allow proper regeneration.
✅ Avoid stop-start city driving and regular short journeys if you own a diesel.
✅ Use high-quality diesel and correct low-ash engine oil.
✅ Fix injector or EGR issues early to prevent excess soot buildup.
✅ Consider getting a petrol, hybrid, or mild hybrid if you mostly do short trips.