On a diesel E320??? Just had mine changed by the dealer and it looks black still....very black , however yesterday i changed the oil on a Nissan Micra (petrol) for a friend and his car was very over due a service around 30,000 miles since it had last been done and the old stuff was very dirty but even without flushing the fresh oil is still honey coloured and a road test I know diesels tend to get their oil blacker than petrols but surely it should stay clean for a few hundred miles ?? How can you tell they have changed it and not just wiped over the filter ??