"Firstly you cant do oil change after every regen as it does at least one regen to every tank full of fuel"
Very true John, Not saying do it after every regen that would be impossible,
I will try and clear up what I meant,
I had same problem as mark I was told by lyles the Italian connection in Newcastle that I needed an oil change and filter then they would do a forced regen which would cure the problem.
I said ok how much ....£185 +vat!!!
Being a tight git i did the work myself for less then £50
when I changed the oil which was only 8000 miles old (car said oil was fine) i noticed there was more oil in there then should have been alot more over a litre more (last serviced by dealer)
But I read somewhere that if the car does not complete many regen cycles then unburnt diesel particals build up
and get into the oil itself (may explain why my oil level was high a litre more then the 4.5L i put in.
but it could have been the last guy to service it, putting to much oil in? dont know).
But what a difference it made putting nice new fully synthetic oil in, the old filter and oil was totally full of soot particals you could see and feel them.
Done that then like i said took it for a good run with out stopping and then it regend its self and car performance went great but with light still on, day later while driving it the MIL light switched it's self off.
I bought a scanner (ms509) checked my car a couple of days after light went out, car had the old code for the EGR fault still in it, so cleared it. checked for any other problems...all clear been great ever since.
This worked for me,that was 2 weeks ago and car is going great.
Only dif was my light was on and i did it on limp mode which was a real pain not being able to go above 60, but still good enougth to do regen