Not just kicking up dust

Since the great pollutant sticker debate in Germany at the turn of the year, particulate filters have seen an enormous rise in interest from car owners. They have been retrofitted in many used cars, and in diesel vehicles they are now considered standard. Once they have been fitted, though, few vehicle owners consider the effects that the filters have on the operation of the vehicle other than the improvement in emissions values.
While filters were still actively plugged by advertisers during the discussions about emissions and taxes, the flow of information has since abated and it lies once more in the hands of vehicle operations to explain about how to care for the filter.

Particulate matter pollutes the environment
Filters that trap particulate matter could be the answer. This particulate is created during the combustion process and comprises combustion remnants and fuel residues (unburned hydrocarbons), sulfur compounds, soot, metallic abraded matter, motor oil and many other constituents besides. It is an unhealthy mixture that has become increasingly apparent in German towns and cities because of the greater frequency of measurement. The rise in particulate matter pollution has in a way been the inspiration behind the particulate filter, because the filter is a match for the greatest cause: diesel fuel.

What a particulate filter does
In a diesel particulate filter the exhaust gases must flow through a honeycomb structure and the particles deposit on the surface of the filter wall. Modern filters regenerate themselves by burning off the embedded particles. Not all residues in the filter are completely destroyed, however: 'The additives contained in fuel and motor oil, and metallic abraded matter in the engine as well, can lead to ash depositing in the filter that is not removed in the regenerative combustion,' explains Harry Hartkorn, an expert from LIQUI MOLY GmbH's Research & Development department. The result is that the permeability of the filter is reduced and the exhaust back pressure increases. The tangible consequences are a deterioration in performance and rising fuel consumption. After a certain mileage, the filter must undergo expensive reverse flushing in the workshop or might even need to be replaced.

There are two ways of delaying this process: Either the manufacturer fits larger particulate filters so that residues can be effectively trapped over longer periods, or the vehicle owner uses particularly high-grade motor oils that burn to leave as little ash and residue as possible.

The influence of motor oil
Sulfate ash from additives containing metal, phosphorus from antiwear additives and antioxidants, sulfur and sulfur compounds are what clog particulate filters the most, explains LIQUI MOLY specialist Harry Hartkorn, adding: 'These substances, known as SAPS for short, must be reduced as much as possible in oils that are used in cars with particulate filters.' Manufacturers call oils that produce low quantities of the above constituents when burnt low-SAPS (or low-ash) motor oils. That is why motor oil manufacturers such as LIQUI MOLY mark containers of low-ash oils as being 'Low SAPS' or 'compliant with Euro 4 emissions standard'. LIQUI MOLY offers a whole array of these special oils for vehicles fitted with particulate filters, including the particularly high-grade TOP TEC 4100 and 4200 line, the LONGTIME HIGH TECH for cars as well as the TOP TEC TRUCK 4050 for commercial vehicles. Workshops can offer their customers the handy 1-liter top-up oil from LIQUI MOLY as a universal aid.

The workshop as a guide
What this essentially means is that the days in which a multipurpose oil from the supermarket could be used in just about any vehicle are finally gone. Following the debate about the use of diesel particulate filters, workshops now have the key task of explaining to consumers the importance of having the right motor oil: An oil that meets the specific requirements of the vehicle manufacturer and does far more than merely lubricate the engine. The diesel particulate filter may no longer be a headline on news bulletins, but for workshops it is more topical than ever!