Oil Ash Becomes A Problem For Particle Filters

2023 Author: Eric Donovan | [email protected]. Last modified: 2023-08-25 09:36

Oil ash from burned engine oil puts a heavy load on diesel particle filters. Novel additives should help in the future.

Almost all new diesel cars are now delivered with a particle filter. The systems hold back carcinogenic soot particles from the diesel exhaust gases. In addition to the soot, which is regularly burned without residue to regenerate the filter, other substances also accumulate in the filter that can become a problem there: so-called oil ash from burned engine oil can clog the structures - with a lower filter effect or even a functional failure than possible Episode.

Lumpy substance

According to Michael Ebert from TÜV Süd in Munich, oil ash is a hard, lump-like substance that is deposited in the exhaust system of a vehicle in places that get particularly hot. This can be, for example, the catalytic converter or the particle filter. “Once that has settled, you can't get rid of it,” says Ebert.

The residues get into the exhaust system because a certain amount of engine oil is always burned with each engine, explains Volker Schittenhelm from the Association of Engine Repair Companies (VMI) in Ratingen. The additives contained in the lubricant are responsible for the residues from the oil combustion, explains Helmut Preiß from TÜV Hessen in Darmstadt.

Different approaches

According to the mineral oil manufacturer Castrol in Hamburg, most additives contain organometallic compounds. When they are burned, the ashes are produced. Additives in the oil should, among other things, provide protection against corrosion, reduce wear, and prevent thickening and deposits. According to Castrol, it cannot be dispensed with. On the other hand, the residues in diesels with a particle filter could lead to the failure of the filter.

The dilemma is to be resolved through the use of so-called low ash oils. According to Castrol, they contain new, low-incineration additives that lead to less combustion residue. Such mineral oils are used, for example, in Audi models that are factory-fitted with a closed particle filter. "Among other things because of the risk of ash formation," confirms Audi spokesman Udo Rügheimer in Ingolstadt. The filling capacity of the filters for ash residues at Audi is designed for up to 250,000 kilometers.

Filter change according to plan

In its FAP diesels, Peugeot uses a filter system that works with additives. A substance is added to the fuel which ensures that the soot that has accumulated in the filter is completely burned off in every operating state of the engine. The systems from other manufacturers require a certain exhaust gas temperature for this, for example. "We accept that the additive will collect as ash in the filter," says Gordian Heindrichs from Peugeot in Saarbrücken.

This would reduce the permeability of the filter over time. But after at least 120,000 kilometers, a maintenance appointment is planned when the filter is changed. so Heindrichs. The filter element is removed and exchanged for a "clean" one. According to TÜV expert Helmut Preiß, oil ash should not cause any problems with retrofit filters either.

According to TÜV expert Michael Ebert, manufacturers currently have to guarantee the functionality of the particle filters for 80,000 kilometers. When the new Euro 5 emissions standard comes into force in 2010, ash residues could become a bigger problem for companies, adds Helmut Preiss. Then namely the durability increases to 160,000 kilometers. (dpa)