Thats what the alfa salesman told me when I bought my mito JTdm. At least once a month drive it like an angry italian. 2 weeks of just doing a 4 mile commute (2 there, 2 back!) resulted in this thing coming on my car, but a quick 20 minute run got rid of it. I do think if this filter is blocked you do lose MPG (supposed to use extra fuel to unclog DPF), so its not always wise to be too gentle with acceleration. I was getting 34mpg on this journey, and this slipped to 29 shortly before it got blocked. Its now back where it was before (and then some thanks to a nice long run). This may sound like a rubbish figure for a diesel, but its such a short slow trip (average 14mph!). My focus 1.8 petrol did <20 on same trip! Average long distance 54, overall 45.