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I am considering purchase a new 2.0l diesel car with a Euro IV compliant engine. I have heard that the particle filter in a modern diesel eventually requires replacement at around 100,000km's and the costs are in the thousands rather than hundreds of dollars.

If true, this could affect my buying decision. Are they really very expensive to replace?

David

From the "Ask jack" archives - 14 December 2009

A very interesting question.

Diesel Particle Filters are relatively new technology and there is still quite a lot of misunderstanding surrounding their servicing and life expectancy.

It can also depend on the Make and Model of vehicle as to how the particulate filter works. Some manufactures for example stipulate a specific engine oil to be used while others add an additive into the fuel system to help clean the filter at specific intervals.

A replacement particle filter can cost thousands of dollars just like a catalytic convertor in a petrol vehicle but their life span is considered to be approximately 200,000 to 250,000km's.

Diesel particle filters trap soot particles. The engine management system controls the regeneration of the filter at certain intervals. Only if this process is not working correctly will the filter itself need to be replaced prematurely.

The engine management system can in some cases utilise an additive, which is stored in the fuel system, and increases the exhaust temperature and burns the soot trapped in the filter. It controls the injection of the additive which means it is used sparingly and only when required. We understand the additive will last between 80 - 120,000km and the replacement cost is about $400.

We also believe the occasional long drive at highway speeds is of benefit to long particulate filter life. I guess if you think the opposite of that theory; a car which travels small distances in dense traffic on a cold engine running a rich mixture is more likely to develop a blocked filter, hopefully it all makes more sense.

Remember also, diesel vehicles incur Road User Charges and the annual Registration costs are higher than a petrol vehicle. Add to that the initial cost of a diesel vehicle which are often higher than a petrol.

We believe in most cases you have to travel around 20,000km as a minimum to gain a benefit from buying diesel over petrol. The big savings come from the better consumption you achieve with diesel so the further you travel the bigger the savings