Maintenance Index

Soot filter maintenance

Filters require more maintenance than catalytic converters. Ash, a byproduct of oil consumption from normal engine operation, builds up in the filter as it cannot be converted into a gas and pass through the walls of the filter. This increases the pressure before the filter. Warnings are given to the driver before filter restriction causes an issue with driveability or damage to the engine or filter develop. Regular filter maintenance is a necessity.

To extend the service interval the use of clean fuel and special lube oil known as: Low SAPS (sulfer , Ashes, Phosphorus and Sulphates,) is needed.

The lube oil consumed by the engine in normal operation is in this tye of oil in a big part gaseous instead of particle matter.

The following aspects influence the service interval :

  • fuel quality
  • lube oil quality 
  • engine maintenance/ condition 
  • load factor of the engine 
  • design of the soot filter (more volume is more ash storage capacity)

The normal ash removal is done by vacuum clean the filter( in protected area), blow out the filter in reverse direction of the exhaust gas and vacuum clean at the same time at the opposite side.

After certain time the cleaning must be followed after a burn in an oven /kiln.

Diesel Particulate Filters (DPFs)

  • Low SAPS oils are specifically designed to be low in Sulphated Ash

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.

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.


The abbreviation SAPS stands for “sulphated ash, phosphorus and sulphur”. A low-SAPS motor oil is therefore an oil with a low proportion of sulphate ash, phosphorus and sulphur. These oils are also designated “low-ash” due to their low tendency to ash formation. The requirement to use low-ash additives in the formulation of modern motor oils may sound simple, but developing this sort of motor oil is a true challenge for every lubricant producer.

Requirements for low-SAPS lubricants are relatively recent. Compliance with stricter emission standards could only be achieved by installing catalytic converters or particle filters. For proper operation, these components required new types of motor oils with a low tendency to form ash deposits and fewer additives containing sulphur and phosphorus. If too many residues remain when the motor oil is incinerated (the laboratory test is performed at 800°C), the fine pores of the diesel particle filter or the vanes of the catalytic converter quickly become plugged and their lifetime decreases drastically. Phosphorus and sulphur are highly poisonous to catalytic converters. They render the surfaces inert and impair the function of removing toxic substances from the exhaust gas in all types of catalytic converters for diesel, petrol and gas engines.

As shown by oil analyses, conventional high-performance motor oils have a high concentration of metallo-organic active substances. For a long time, the standard wisdom was that the more calcium, magnesium, boron, zinc, and (of course) phosphorous and sulphur a motor oil contained, the better was its alkali reserve (BN), and thus the better the oil. After all, the additives are what provide high wear protection and good engine cleanness. The proportion of additives has been significantly reduced due to exhaust after-treatment. This was made possible by using low-sulphur fuel and by modern oil technology and engine technology. In this way, emissions of harmful substances have been markedly reduced. However, it was necessary to develop entirely new additive packages in order to combine this with fulfilling increasingly demanding requirements for longer oil change intervals, less friction, and good wear protection.

The trend is inevitably heading toward increasing use of low-ash, low-SAPS oils. This is also reflected in the specifications of the Association des Constructeurs Européens d’Automobiles (ACEA) and the specific oils approved by vehicle manufacturers. ACEA E6 motor oils for utility vehicles are allowed to have a maximum ash content of 1.0%. Since 2004, ACEA C1 to C4 also take this into account for passenger cars. They all specify significantly reduced proportions of ash-forming substances in motor oils as a prerequisite for achieving a longer useful life of catalytic converters and particle filters.

Using low-SAPS motor oils is particularly imperative with modern vehicles. However, when selecting a suitable motor oil you should always observe the specifications or oil types approved by the engine manufacturer in the operating manual. Modern oils only work properly with the fuels specified in the EU, which are designed for modern engines with their exhaust aftertreatment systems in cooperation with low-SAPS oils.

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