Thanks kfk, I take your comments on board. After washing the filter there was a considerable amount (maybe more than 1 litre) of "ash" that had been washed out of the filter, this I suspect, was one of the main causes of the filter blocking up. There did not appear to be any evidence of the Eolys fluid causing any blocking, but I could only see the two filter ends and obviously not inside the actual filter element. Just one question that comes to mind, if Citroen do send these filters away to have them cleaned, then it must be a physical process to remove the "ash". Subjecting the elements to high temperatures I don't think will remove the "ash". The "ash" is the result of the soot particles and presumably some of the fluid being burnt. Anyway, time will tell as to the general success rate. I know the author of the original posting, informing of the washing method, had run his vehicle for several months without problems whereas before he was being subject to all sorts of warnings and limited revs.