Originally Posted by Rob 156
Some oils do this, my dad had his 320td serviced by bmw, only to find the oil was black. The mechs insisted that this new synthetic oil turned black pretty much straight away. My dad wouldn't have it, so they changed the oil again in front of him. I saw him two days later, and he showed me that the oil already looked like it had been in there for ages!
Diesels tend to discolour oil very quickly. My wife's X5 3.0D turns the oil black in a couple of days after a change (ditto for my Kubota tractor)
