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DPF (Diesel Particulate Filters) Explained

Learn all the Facts! Why you need a Compatible Engine Oil...

A DPF is a common part of a vehicles exhaust systems these days, however not many people know what they do, and fewer know that you have to have a compatible engine oil to ensure no damage or blocking occurs.

Shop For DPF Cleaner

What is a DPF / Diesel Particulate Filter.

The diesel particulate filter (DPF) was introduced in 2009 to ensure diesel engine'd vehicles met the emission requirements of "Euro 5". This standard aims to deliver an 80% reduction in soot and so massively reducing the amount of physical pollution into the atmosphere.

The filter, in essence, is a fairly straightforward idea of just trapping the larger soot particles within the exhaust system (basically like a area of meshing that acts like a net to capture the particles) while still allowing gasses to escape through and out. Once the filter becomes full or at the specified level (normally around 40/45%) then "regeneration" occurs, which is a burning of the soot within the filter to reduce it down to a more manageable finer ash residue, this "regeneration" takes the place of physically emptying it.

Need to clean your DPF? Why not buy Millers Oils Diesel Particulate Filter (DPF) Cleaner & Regenerator

Regeneration of the DPF occurs in two types of way, either passive or active.

  • Passive: this automatically takes place during prolonged fast placed driving were exhaust temperatures reach a high enough temperature to burn the soot down, a good example would be a good hour or more trip on a motorway.
  • Active: because not everyone is guaranteed to do enough fast paced driving to passively burn down the DPF soot, "active" soot management happens. This is automatically done by a vehicles ECU and is done by fuelling after the combustion process and allowing the fuel to go through the exhaust to burn the soot build up.

Where are they, and how do I check if I have one?

Although the diesel particulate filter (DPF) was introduced in 2009, many vehicle manufacturers were already producing their cars / vans etc with the filter in place, this was in anticipation of the change in standards... so simply ruling out your vehicle because it was produced before 2009 isn't enough.

As you'd expect this filter is part of your exhaust system and comes in all manner of shapes and sizes, however most commonly looks similar to a catalytic converter, or large vertically fitted cylindrical item at the back of a vehicle engine block... so pretty annoying to spot and confirm.

Check your handbook, this could possibly be the easiest way to determine if your vehicle has one fitted as generally they'll have a whole section dedicated to Diesel Particulate Filters and which vehicle models are fitted with them.

Engine Oil & your DPF.

One thing that is worth note: if your vehicle isn't able to perform a full DPF "active" regeneration process and a warning light appears on your dash. This means over fuelling is occurring and it's recommended you continue your journey for a further 10 to 15min at speeds around 40mph to allow the ECU to finish the process. Failing to allow this can leave fuel within the piston cylinders that can drain into a vehicles sump severely damaging the integrity of your vehicles engine oil.

Within the combustion process a small amount of engine oil is burnt off (don't worry this is by design), hence why you need to regularly check and top up levels in-between services. These burnt off bits of oil could potentially, and very quickly, block or permanently damage a DPF (through physical particles and DPF damaging burnt oil gases). This is where a Low SAPS (Sulphated Ash, Phosphorous, Sulphur) motor oil comes in, it's basically a low Sulphated Ash, Phosphorous and Sulphur based oil, if a normal engine oil was used these elements would quickly block and the gases would terminally damage the intercut internal of a DPF.

So you need a Low SAPS engine oil, what now? well a good place to check would be your handbook, you'll most likely find an Acea Specification engine oil is recommended by your vehicle manufacturer. Once you know the spec use the links below to go shopping, remember the most important thing is the spec, once you've got the correct range of oils in front of you it boils down to personal preference and budgeting restrictions

Go shopping for Acea spec engine oils:

If you're unsure of which engine oil, or how to find a Low SAPS diesel particulate filter (DPF) compatible engine oil, then why not use our engine oil lookup page.

Replacing a DPF is expensive, ensure you use the correct oil to keep it clear and blockage free.

MOT: Remember not having a DPF present on a vehicle that was manufacturer with one will result in MOT failure (since February 2014).