Diesel particular filters or DPFs have become the solution of choice for many manufacturers to deal with soot and ash when diesel is burnt. Basically they are a filter in the exhaust that collects soot and stores it to be processed during a DPF burn.

DPF delete

 We are all about performance and we all know that any restriction will reduce the performance of an engine. So what can we do about the DPF? What is it and how to look after it?

The DPF can be deleted from the exhaust and the software. This is the simple solution to all the issues caused by having a DPF. I am not going to go into all the legal stuff of removing an emission related device. I am simply saying that is the simple solution.

One good thing for a DPF is reducing soot getting  into the atmosphere. Some would say a benfit for the environment. Now that is a vague statement at best. It is necessary for a DPF to regenerate or burn off the soot periodically. The way this is achieved is to make the DPF hot enough to burn off the soot so it can pass through the filter. One way this is done is the ECU injects addition fuel to generate the addition heat in the filter to burn off. Doing this obviously uses more fuel (not good for the environment), and an amount of this additional fuel also finds its way into the engine sump diluting the engine oil which can mean additional oil and filter changes.
Similar to when catalytic converters when introduced and lead was removed from fuel because it would foul up the converter. Vehicle with DPFs require special oils that are low in sulphated ash, phosphorus and sulphur (low saps). The use of incorrect oil will block the DPF and prevent regeneration making it necessary to replace the DPF. One ugly point of DPF is the cost to replace.


Low and Mid Saps oil

Some say that the oil requirement for the DPF makes the internal engine wear rates higher than if a normal oil was used. We will debate that another day.
A real problem we see with DPFs is when a boost leak occurs. A boost leak will cause extra soot in the exhaust and block the DPF quite quickly. Once the boost leak is fixed a DPF clean will almost always be necessary. We can do a DPF clean with the DPF still fitted to the car. Once the DPF clean has been performed a regen can occur. Whenever it is  necessary to perform a forced regen an engine oil change is required after the regen. Why, remember before how extra fuel is injected to get the DPF hot enough to regen, this extra fuel will dilute the engine oil.

So what is a forced regen anyway? Forcing a regen is a using a scan tool to command a burn while the vehicle is stationary. Often a forced regen will use higher temperature and the regen tool will monitor the pressures in the DPF during the process. Special tools are required to perform a forced regen so your average mechanic may not be able to perform this. But be aware you do not have to use the dealer. We like a number of well-equipped workshops do have the equipment to perform the forced regen.
In more extreme cases a forced regen will not be possible due to the amount of soot loading. The next step in the process is an on car clean. Our on car cleaning tool is a two step process. A cleaner is injected into the DPF and processes the soot over a given time. The cleaner is then purged from the system which leaves the DPF ready for a forced regen. The on car cleaning equipment is even less common for a workshop to have. We can also help with on car DPF cleaning.

Liqui Moly DPF cleaner kit


So you have a DPF, how do you get the best performance and life from it.
Regular maintenance of the vehicle is a given. Normal servicing using the correct engine oil.
Years ago I was never a fan of additives. Now a number of additives or cleaners do have a place with modern cars. A DPF cleaner added to the fuel every 5 to 10k reduces the temperature and time for a DPF burn to be completed.
When the DPF burn lamp comes on and it will come on you are best to let the burn occur. Putting the burn off could make it necessary to perform a forced regen or a DPF clean.

This is just a brief overview of the DPF and some of the pros and cons related to its use.

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