I have a 3.0-litre diesel BMW X3 that does 12-15k miles p.a. on a reasonable mix of long and short runs. After 5yrs/65k miles BMW are telling me the DPF needs replacing. The car suffers from an intermittent loss of power, particularly when trying to overtake from say 60-80 mph. Basically, I am not convinced that the DPF is the root of the problem or that replacing it will produce anything other than a short term improvement at best.

Apparently, the engine diagnostics say the DPF is partially blocked (no warning lights are showing) and repeated attempts by me and BMW to do a forced regeneration have been unsuccessful. Supposedly the "back presssure" is too high or low to allow regeneration to take place even when the car is set up to force a regeneration to occur.

If the DPF has reached the point of no return it seems to me that there must be a pre-exisiting problem that caused the DPF to reach this point i.e. regens have not been occurring for some time to keep the filter clear.

The BMW dealer cannot explain the problem, except to say my driving profile must have changed (it hasn't!). BMW UK will not give access to their technical gurus unless requested by the dealer (they won't!). Result is impasse unless I spend £1200 for a new DPF. I have happily driven BMWs for 30 years, but this is certainly making me think twice about the car and BMW diesels in particular.

Do you have any suggestions about what my problem could be and/or what I should do next?

Many thanks.