As I understand it, DPFs require a periodic regeneration cycle where fuel is
injected during the exhaust stroke which then burns in the filter. This raises
the filter temperature to the point where the particulates burn off.
The regeneration cycle occurs roughly once per tank of fuel and requires a
warm engine and several miles of driving to complete. I know this because the
effect on my XC60's instantaneous fuel consumption makes it pretty obvious
when it's happening!
So a DPF-equipped car which is used for mainly short journeys *might* be
susceptible to the filter getting clogged because either the engine fails to warm
up sufficiently for the cycle to start, or the cycle is interrupted prematurely.
This is the reason why we plumped for the T4 V40 rather than the diesel
version, since it is used primarily for short journeys.
I have no idea if this accounts for the difference in used prices of V40s.
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