Diesel cars have had a rough time in the press over the past few years, but the truth is that a well-maintained diesel engine is still a brilliant choice for high-mileage drivers. The key word there is well-maintained. Modern diesels have some extra components that need looking after, and ignoring them can lead to some very expensive bills.
What Is a DPF and Why Does It Matter?
The Diesel Particulate Filter (DPF) is a filter in your exhaust system that catches soot particles. It is a legal requirement on all diesel cars built after 2009, and removing it is illegal and will fail your MOT.
The DPF cleans itself through a process called regeneration — the engine raises the exhaust temperature to burn off the trapped soot. This happens automatically when you drive at sustained speeds (typically above 40mph for 15 to 20 minutes). The problem is that if you only do short trips around town, the DPF never gets hot enough to regenerate, and it gradually clogs up.
Signs Your DPF Is Blocked
The first sign is usually the DPF warning light on your dashboard. You might also notice a loss of power, higher fuel consumption, or the engine going into limp mode (limited to around 3,000 rpm). If you catch it early, a good motorway run can often clear it. If it has gone too far, you will need professional cleaning.
How We Clean DPFs at AVS
We use state-of-the-art TerraClean machines to clean DPFs without removing them from the vehicle. The process takes about an hour and costs from just 125 pounds plus VAT — compared to 1,000 pounds or more for a replacement DPF. TerraClean uses a patented cleaning solution that breaks down the carbon deposits and flushes them out safely.
What About the EGR Valve?
The Exhaust Gas Recirculation (EGR) valve recirculates a portion of exhaust gas back into the engine to reduce emissions. Over time, it gets clogged with carbon deposits, especially on cars that do lots of short journeys. A sticking EGR valve can cause rough idling, poor performance, increased emissions, and the engine management light to come on.
We can clean EGR valves as part of our TerraClean service, or replace them if they are beyond saving. Cleaning is always our first recommendation — it is cheaper and often just as effective as replacement.
Tips for Keeping Your Diesel Healthy
Drive it properly at least once a week. If your daily commute is short stop-start driving, try to take the car for a 20-minute motorway run once a week. This allows the DPF to regenerate and keeps everything running cleanly.
Use good quality fuel. Premium diesel from the major brands contains cleaning additives that help keep injectors and the fuel system clean. It is worth the few extra pence per litre.
Do not ignore warning lights. A DPF light that is dealt with early is a 125 pound clean. A DPF light that is ignored for months becomes a 1,500 pound replacement. The same goes for the engine management light.
Keep up with servicing. Regular oil changes are especially important on diesels because the oil gets contaminated with soot more quickly. We recommend changing the oil every 12 months or 10,000 miles, whichever comes first.
The Bottom Line
Diesel engines are not difficult to look after — they just need a bit of understanding. If you are having any issues with your diesel, or if a warning light has come on, bring it in and we will diagnose it properly. Our DPF and EGR cleaning service has saved hundreds of customers from expensive replacements, and we are always happy to give honest advice about whether cleaning or replacement is the right option for your vehicle.
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