Top notch HDEO oils which are C rated can easily handle extra soot so if need be, they can be stretched safely beyond limit to an extent but if changed at the recommended interval, they offer a degree of protection like no other. My turbo OM616 has been on either Delvac MX or Delo 400 since the beginning and the internals are spotless after 125,000 miles of real hard use off road, in extreme summers at 48C temps outdoors. The compression test gives the readings which haven't varied much from a new engine and oil consumption is very minimal.

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99 Gurkha with OM616 IDI turbo

2015 Gurkha with OM616 DI turbo

2014 Rexton W with OM612 VGT