Can too much DPF Additive damage your engine?

Regular short journeys, continuous slow speeds, or an engine fault can cause a DPF to become overwhelmed with soot. While faults must be rectified by a workshop, fuel additives can help compensate for less than ideal driving conditions but only if you use them correctly.

What is a DPF?

A diesel particulate filter is part of the exhaust system and traps cancer-causing soot before it pollutes the air.

It empties periodically by heating up and burning off the soot. This process is called regeneration.

If the DPF cannot reach a sufficiently high temperature, soot will accumulate, causing a partial blockage. This raises pressures within the exhaust system, which the engine has to overcome.

Excessive soot buildup can lead to even higher pressures, which can damage the engine (and/or its ancillaries) and prevent it from running properly.

How do I know that my DPF is about to block?

You may receive a warning message on the dashboard, prompting you to take the car for a longer drive to allow the DPF to regenerate. If you ignore this instruction, the soot will continue to build to such an extent that the car may be unable to resolve the situation.

This tends to cause an engine Management Indicator Light to appear, with their resultant drop in power, and you will need a garage (or even breakdown assistance) to help you. Continuing to drive will cause the filter to fill completely, which could stall the engine.

What causes a DPF to block with soot?

· Ignoring warnings to take the car on a longer, or faster, trip.

· Excessive start/stop city traffic driving, especially in colder weather

· A fault that causes the yellow engine Management Indicator Lamp to illuminate

· A leaking engine intake system

· Driving with a low fuel level

When might I need an additive?

Should your situation make it very difficult to take the car on an extended drive, such as you living in a busy urban area, you can consider a regeneration-aid fuel additive.

These products contain chemicals that envelop carbon, making it easier for the soot deposits to burn and, therefore, reducing the DPF’s pressures.

What additive should I use and when?

Most regeneration additives are designed for use, when the car displays its first blockage warning.

They tend not to be designed for DPFs that have become so blocked with soot that an orange Management Indicator Lamp has been triggered. If this happens, consult a garage and tell the technician if you have used any additives.

It is a good idea to retain the bottle, so the workshop is aware of any previous attempt to repair the problem.

Do DPF cleaners work?

As there are so many diesel fuel additives on the market, it is very difficult to say. Some of them are intended as preventive measures, such as fuel injector cleaners, which are useful for vehicles that cover very low mileages.

Others are designed to resolve light DPF blockages, only. Read the instructions and align the product with what you are trying to achieve. Overall, DPF regeneration additives that clear soot tend to work well but some of them work better than others. The last thing you want to do is damage an expensive DPF.

DPF cleaner formulas are closely guarded secrets. Generally, we find that additives containing iron are not as effective as the more expensive types that possess cerium-based ingredients.

How often should you use DPF cleaner?

If you undertake longer trips, drive frequently at over 40mph and your car lacks any major faults, your DPF’s regeneration should be undetectable.

Should your driving cycle be less than ideal for a successful regeneration, follow the additive maker’s recommendations for usage frequency. This is because some DPF regeneration aids also function as fuel system cleaners, which is beneficial no matter how you drive.

What happens if I add DPF additive to a half tank?

Problems can occur not due to the additive itself but because the dosing instructions are ignored. If the directions say to add the bottle’s contents to half a tank of fuel, and you do so, there should be no problem.

However, if you double dose, by either adding a product that requires a full tank to half a tank, or by using multiple bottles, the additive/fuel concentration is higher and this promotes even greater temperatures within the filter.

This is not recommended for two reasons. Firstly, the filter’s internal structure can overheat and melt, rendering the DPF useless. More seriously, the DPF’s exterior might fail, causing red-hot particles to fall out and ignite material on the floor, risking a vehicle fire.

Therefore, should you choose to use a DPF fuel additive, pay close attention to the dosing instructions. More 'medicine' is definitely not the best remedy in this case.

How can breakdown assistance help with DPF problems?

As always, prevention is better than cure and so we would advocate not tempting a breakdown by ignoring the DPF regeneration message.

However, should a DPF blockage cause a lack of power or a breakdown, GEM Motoring Assist’s team will be by your side to help.

DPF Additive Q&As

How do I know when my DPF needs to regenerate?

Regeneration should start and finish without the driver knowing. If multiple regenerations are aborted, the car will alert the driver.

Yet, as there is no standardised message, consult your car’s handbook. Some vehicles display a warning symbol, such as that pictured. Others show text.

What do DPF ‘regen’ fuel additives clear?

These additives promote higher temperatures, so accumulated soot/carbon particulates can burn in a controlled manner. This results in the filter emptying safely and reducing the pressures.

Do DPF additives clear ash?

No. Ash is a natural byproduct that accumulates in the DPF over many years. Manual cleaning is the only option, comprising physical removal and backwashing with special chemicals that do not damage the structure.

Should I perform a forced regeneration, rather than use an additive?

Forced regenerations are performed by garages. They are stressful on the DPF and the engine. We recommend that, if possible, forced regenerations should be avoided and you should look at resolving any light DPF blockages as soon as you are prompted by the car.

This might include using an additive and dosing it as directed.

How can the DPF block quicker than usual?

DPFs can block very quickly, if there is an engine, or fuel system, fault. Ignoring service intervals and using the wrong oil are also problematic for DPFs. For advice on what oil your car needs, check-out this blog.

Can I not just remove the DPF?

We do not advocate removing the DPF, because it is against the law. For more information, see our advice here.

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