Diesel Particulate Filters (DPFs)

DPFs – How do they work?

Many modern vehicles are now fitted with exhaust systems that minimise the emissions of the vehicles – this helps reduce the impact on the environment of running these vehicles – a key objective for vehicle manufacturers.

All internal combustion engines burn some level of oil by design – even the most modern. Inside a DPF is a ‘mesh’ like structure, which acts like a ‘net’, capturing the harmful soot particles produced by a diesel engine that would otherwise be emitted into the environment. As these ‘nets’ become full the DPF must clean itself out in order to continue working properly – a process known as ‘regeneration’. The exhaust system burns off the soot particles so that while there is still some waste, it is only a fraction of what it would otherwise be.

In order for this ‘regeneration’ to occur the exhaust needs to heat up considerably. This is typically achieved through motorway type driving although some vehicles have the capacity to force the exhaust system to get hot without such driving by adjusting the injection timing via the engine management system.

It’s this issue of ‘re-generation’ that has attracted come complaints from motorists recently – see the BBC Watchdog feature here.

DPFs – you must get the right engine oil

It’s not just about how you drive the car that affects the DPF though. Another key issue to be aware of is getting the right oil for cars with Diesel Particulate Filters. All internal combustion engines, even the most modern, still burn some oil – one reason why 1 in 3 vehicles in the UK has a low oil!

Low SAPS oils

When the oil burns in an engine, naturally it emits some gas but some of these gases could be harmful to a DPF. Low SAPS oils are specifically designed to be low in Sulphated Ash – a by-product of combustion that can cause the ‘mesh’ structure in a DPF to become irreversibly blocked. Such oils that are not low in Phosphorus and Sulphur can also have a significant, detrimental effect on Catalytic Converters – so the issue of getting the right engine oil is relevant to petrol and diesel vehicles alike.

How to find a Low SAPS oil

One way to identify a Low SAPs oil is to look for an ACEA ‘C’ classification – C1, C2, C3 or C4 (It doesn’t necessarily follow that C1, is better or worst than C2, C3 or C4 – they are just different). ACEA (The European Automobile Manufacturers Association) sets standards for engine oils in Europe and its specification for Low SAPS oils begins with a ‘C’. However, most vehicle manufacturers have their own specifications for Low SAPS oils which can make the job of identifying the right oil for your vehicle quite complicated.

An easier and safer way to make sure you’re getting the right engine oil is to use Comma’s online recommendation service. By entering your vehicle registration or selecting your vehicle from the list, we’ll tell you which product you need. What’s more, we guarantee every recommendation we make. You can find the right oil for your car by using the vehicle lookup.

If you’d like more advice or if you have a question about a specific vehicle, then please feel free to contact our Technical Team.