DPF Cleaners and DPF Cleaning – The Definitive Guide
This is the second iteration of this article. It has been updated to reflect the common problems that are encountered when tackling what are understood to be DPF blockages.
In this article we will address the following questions:
- What is a DPF?
- Why do DPFs clog up?
- Misdiagnosis and related common faults.
- Reasons why a DPF cleaner may not work for you?
- The correct logical steps to diagnose and fix a DPF blockage.
What is a DPF?
A DPF or Diesel Particulate Filter is a device integral to the operation of the exhaust emission control system. It captures particulate matter and hydrocarbons, stores them, and every so often a process of regeneration occurs where these deposits and particulates are burned off, converted to CO2 and vented out the exhaust.
Why do DPFs clog up? There are a number of contributing factors.
The first is the quality of the fuel. The second is the quality of the engine oil and the third, driving style and journey type. Diesel engines in particular are not designed for short journeys or stop-start driving and such conditions create an excess of particulate matter in the emission control components. That means that the DPF as well as other parts such as the EGR and catalytic convertor have more particulate waste to deal with.
The issue arises when the engine is producing more particulate matter than the DPF can cope with. A variety of symptoms may then become evident such as engine hesitation or power loss. Eventually an engine warning light that informs you there’s an issue with the system, and if not resolved the vehicle is then put into a “limp home” mode, with reduced power.
If the system is clogged excessively, it is common for the ECU to prevent further regeneration. This is very lucrative for some dealerships and garages, because in their view, it means you have to replace the DPF, which can run four figures in cost. I can tell you categorically, the DPF can be cleaned unless it has failed catastrophically, even if it’s 100% saturated and the vehicle will barely run at idle. It can also be cleaned even if the ECU will no longer force a regeneration cycle with the help of diagnostic software. Furthermore, modern cleaning techniques and technology means that the DPF does not have to be removed to be fully cleaned but more on that later.
It is important to note that particulate matter that accumulates in the DPF is NOT just from the fuel and the combustion process. It’s normally a combination of those elements, as well as engine oil. Oil can be blown through the crankcase breather system, but more commonly (on a diesel engine), it bypasses the piston rings and is poorly combusted. Those particulates then accumulate in the DPF. This is the reason you have mid-SAP and low-SAP oils. The theory is that such oils have lower ash content, which gives the DPF an easier life. In some cases, high ash content can damage the DPF because it isn’t able to combust those types of particulates. Our experience actually differs from this as higher ash oils can prevent oil being bypassed in the first place. However, that is a different subject for another day.
Resolving a Blocked DPF
Firstly, one of the most common mistakes is actually misdiagnosis. An emission control warning light or even a DPF warning light does NOT ALWAYS mean the DPF is blocked. This is much more common than you think so do not assume the DPF must be blocked if your vehicle produces a DPF warning light.
- Emission warning lights are normally shared across the entire emission control system so an EGR (exhaust gas recirculation) valve fault or similar can be the root cause of what first appears to be a DPF issue.
- One of the most common faults is that the Pressure Differential Sensor that calculates the saturation level and reports an over-saturation condition to the ECU could be faulty. In other words the DPF is fine but the sensor is reporting excess carbon and preventing a regeneration cycle. These sensors should be one of the first things that are checked but they are often ignored. The result is an unhappy customer as the cleaning product or process “didn’t work”. It probably did but the sensor is just reporting otherwise.
- The ECU has identified the pressure sensor as faulty and it is this that needs to be replaced rather than the DPF cleaned.
Secondly, and more important than the first; there MUST be an underlying reason for a DPF blockage if, in fact, it is actually blocked. The underlying reasons should be established and where possible, addressed accordingly.
- Fuel system deposits resulting in an inefficient combustion process can produce more carbonaceous matter than the DPF can manage. This can also apply to using low quality or incorrect specification oil. Is the engine consuming oil?
- Driving style and journey types. Certain conditions must be met to enable the DPF to regenerate and manage the carbon build-up. Continuous low RPMs, stop/start driving and short journeys that do not permit the engine and DPF to reach full operating temperature will eventually take its toll.
- Other underlying faults such as an injector or EGR issue could be preventing the DPF from regenerating. The ECU recognizes an underlying fault and “locks out” or prevents DPF regeneration cycles.
- As above, the pressure differential sensor is just faulty and misreading the level of backpressure between the front and rear of the DPF. Saturation level is only 10% yet the sensor is calculating 50% = game over until the sensor is replaced.
Therefore, as best as you can it is important to establish if there is a DPF blockage and if there is, or high probability that there is, to identify the root cause(s). If not, you will be fighting a losing battle.
This is why fuel-based DPF cleaners and professional DPF cleaning is so hit and miss. Many users fail to correctly diagnose and/or address the actual root cause.
If a fuel based DPF cleaner did not “work” then there is a good chance that the actual fault is not directly DPF related or that an underlying problem is forcing you into lose-lose position. It is not always as straightforward as many make out but I am going to make it as easy as I can for you.
Logical Steps to Resolving Suspected DPF Issues
||If you suspect the DPF is blocked then before you spend a penny on diagnostics or treatments do this: Get the vehicle up the full operating temperature, drive down the road and drop a couple of gears to get the engine revs above 3-3.5k. In other words try to force a DPF regen.
||Free other than the cost of fuel
||If the above fails then you need to make the choice of using a fuel based cleaner and/or investigating further. If using a cleaner then combine it with step 1. It is a reasonable low cost process of elimination. I would recommend a high strength fuel system and engine cleaner first before using a dedicated DPF Cleaner OR use a fuel cleaner with combined DPF cleaning function. A basic OBD / CAN BUS code reader can be purchased for as little £10-£20. I recommend everyone keeps one in their car. If warning lights are visible then the ECU will have stored codes and rather than blindly guessing you are well on your way to correctly diagnosing the issue or any underlying problems.If the codes do indicate a DPF saturation issue then this may be enough to justify using a high quality fuel cleaner and/or dedicated DPF cleaner. The rationale for using a fuel cleaner first is that it will ensure the fuel system is clean (common underlying fault) whilst also helping to clean the DPF by restoring combustion efficiency. Many fuel system cleaners and carbon removers also include catalyst technology that will actively remove carbon from the DPF anyway.Please don’t hesitate to contact us if you need help with interpreting error codes or advice on correct product choice.
||High Quality Fuel Cleaner – £20
Code Reader – £10+
Dedicated DPF Cleaner or combined Fuel and DPF Cleaner- £20+
|3. Professional Diagnosis – Basic
||If you don’t have a code reader then a diesel specialist will be able to read the codes for you, leaving you with the choice to attempt the fuel cleaner based route should the codes point to a genuine DPF blockage issue.If the Technician has the correct diagnostics tool they should be able to attempt to force a regeneration cycle either on its own or aided with an in-tank DPF cleaner.
||Basic Code Reading – £20+Forced Regen – £30+
|4. Professional Diagnosis – FULL
||A full diagnosis should include a full error code check and a test of the pressure differential sensor as well as other emissions control components that can create an apparent DPF issue. Basically, you want to confirm if the DPF is genuinely blocked and if so, why? Or the technician needs to identify the actual underlying fault(s) creating the warning lights.If it is looking like a DPF blockage then the first step is for the technician to attempt to force a regen cycle via the diagnostics tool. This is by far the cheapest fix before professional cleaning or worse, DPF removal.
||Full Diagnosis – £60+Plus any remedial treatment/repair costs.
|5. Professional DPF Clean
||If other underlying faults have been ruled out, a DPF blockage correctly diagnosed and a fuel system cleaner plus DPF cleaner hasn’t worked then a professional clean would be the next logical step.Our recommendation would be a professional DPF Cleaning Kit. These are professional use products so you will need to find a participating garage. This is a non-invasive process and is fully guaranteed. The garage will require the correct equipment to reset the DPF and where necessary force regeneration once cleaned.
||Professional DPF Clean £200+
In many cases, using a professional fuel system and carbon cleaner to ensure that the fuel system and injectors are operating without deposits can be more important that using a dedicated DPF cleaner. Not only will a fuel system cleaner help clean the DPF anyway but it will eliminate one of the most common contributory factors (dirty injectors) that if not resolved, will allow the DPF to clog up again soon after. For this we recommend the new Archoil AR6400-D MAX as it is a combined fuel system cleaner, carbon remover, turbo cleaner and DPF cleaner.
You can use a generic cleaner that relies on the natural scavenging and cleaning mechanism (as described in the EGR cleaning article) or you can utilize one of the higher-end cleaners that use molecules that are activated during the combustion process (catalysts). These molecules bond with the hydrocarbons in the DPF and reduce the threshold temperature at which they can burn. By far the best we have tested is the Archoil AR6400-D MAX. It contains chemistry comprising of carbon-removing molecules that are activated during the combustion process rather than destroyed like most fuel additives. This type of cleaner combined with a spirited drive (or dropping down a gear) to create more heat will help to clean the DPF much more thoroughly. In genuine DPF blockage cases, these cleaners have some of the highest success rates of any DPF cleaning additives we have tested of reducing the saturation percentage, removing the engine warning light and enabling passive regeneration.
It’s important to point out that heat is vital when removing carbon. So, using such a cleaner with short journeys will inhibit results. You have to combine them with a longer run, and a driving style that permits the temperature within the DPF and the system in general to increase.
If passive regeneration is not restored and the cleaner is not working then the DPF is oversaturated to the point that the ECU will not permit a regeneration cycle, the issue has been misdiagnosed or there is another factor restricting DPF regeneration. DPF regen could be locked out by the ECU rendering the system inoperable. It is also possible to have a vehicle that’s so saturated that the back pressure is restricted so much that it will barely idle. For this, the DPF needs to be cleaned directly by a professional.
It usually consists of a 2 step cleaning process that must be administered by a professional. The first of this series is sprayed directly in the DPF through the pressure sensor hose. The chemical bonds with the carbon, dissolves it and prepares it for the next stage.
The second step involves holding high revs to burn off the carbon for a few minutes, followed by a flushing solution administered through the same hose. This removes any residual cleaning agents and deposits.
We recommend finding a garage local to you for this type of clean.
Maintaining a Clean DPF
Once the DPF is clean, it’s equally important to ensure that the particulates remain at a manageable level. I’ve already mentioned the importance of a professional fuel system cleaner to restore efficiency in the fuel injectors. I’d also recommend an ongoing fuel additive that contains a fuel catalyst or combustion modification technology, such as Archoil AR6900-D MAX or Oilsyn Hybrogen. They will lower the amount of hydrocarbons created in the first place. They reduce the threshold temperature at which the fuel is burned even when the engine is cold. So, even from the moment you start the engine you’ll be producing fewer hydrocarbons. This is critical if your vehicle is just used for local trips (shopping runs, school runs, etc.). It gives the DPF a much easier life and will reduce the tendency for it becoming oversaturated in the future. We have many reports from both consumers and fleet owners that their vehicles regenerate much less when using Hybrogen or AR6900-D MAX. The key is to keep the carbon production at a manageable level for the emission control system and such additives achieve this.
Excessive Oil contamination
If the engine is consuming oil then unburnt oil can contaminate the DPF. Where necessary, use a professional engine oil flush to restore lost compression during the next oil change as deposits build up on the piston rings. These deposits push the rings away from the bore, thus allowing oil to bypass the rings and enter the combustion area. Once that happens, the DPF has to cope with an influx of particulates and more buildup.
Then use a high quality oil and/or oil additive to retain correct compression and prevent any future deposit build-up. For this we recommend any genuine synthetic oils (group IV or better) and/or Archoil AR9200 or AR9100. This will keep the piston rings and bores clean and reduce the amount of oil entering the intake. Combine this with a fuel additive, and there’s no reason the DPF cannot outlive the vehicle itself without the need to use dedicated DPF cleaning procedures (invasive or otherwise).
I hope that helps. If you require any assistance then please don’t hesitate to contact me or a member of my team.
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