Car: 2007 1.8ES i-shift
Join Date: 8th July 2010
Location: Tenterden, Kent
Thanked 9 Times in 9 Posts
My understanding of how a DPF works (from previous experience with 2 DPF equipped cars) is that all cars with a DPF will regenerate (ie: as said above, help themselves to your diesel) every 200 - 500 miles, dependant on use. A DPF only becomes clogged if this regeneration cycle doesn't occur.
In order for regeneration to start, a number of conditions have to be met (ie: determined by sensors in the engine); the most critical of these is that the cycle won't start until the engine has reached full operating temperature and the revs are above tickover.
Therefore DPF diesel's doing lots of short runs are more liable to DPF problems - either because the engine never reaches operating temperature, or because although the cycle may have started, it doesn't complete due to the engine being turned off too soon. Generally speaking, for a DPF regeneration to successfully complete (especially in winter) the engine needs to run for at least 20 minutes from cold. If my understanding is correct; if the engine revs go down to idle for more than 30 secs or so, the DPF cycle will stop; even though it hasn't completed.
Please don't think I'm scaremongering here, but having run an Alfa diesel (that many owners had expensive DPF issues with), I read all I could about them to try and avoid problems myself. By always having the instantaneous fuel consumption displayed on the trip computer I could see when a DPF cycle started and found it was best to drop a couple of gears to build the revs up while the cycle completed (regeneration works by creating unbelievably high temperature within the DPF to burn all the crap off - talking several hundred centigrade). I never did have any problems with my DPF but always lived in fear of them; hence why I now drive a petrol even though I love diesels!