The DPF on my BMW 5 Series is blocked - can I add something to clean it?

The DPF on my BMW 5 Series is blocked. Can I add something to clean it as I only do short journeys, or should I give the car a good run on the motorway?
There are products that claim to help such as Cataclean but I have received no independent evidence. If you drive long distances regularly the DPF will passively regenerate. If you drive short distances it will try to actively regenerate and this doesn't always work, especially if you switch off mid-regen.
Answered by Honest John on

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