Originally Posted by Graham

If car was not maintained by a dealer, it might be of interest to know what oil was used. The oil specified for the Bluetec is a low-ash oil. If an owner or his garage has not used the correct oil, then that could be part of the problem. You can't just put any old diesel oil into the Bluetecs. High temperatures in the emission system can increase sludge formation which in turn can cause engine failure. I believe it must be to MB-Approval 229.51 or 229.52.