The DPF is not actively regenerating and instead the extra diesel injected into the engine to promote regeneration is sinking into the sump. It urgently needs to be drained out and replaced to the correct level. Diesels can blacken their oil very quickly, but there is something wrong with yours. If the supplying dealer won't fix it, write a letter to the dealer principal expressing your misgivings and demanding he take the car back and fix it. Send this by post office special delivery, keep a copy and staple the certificate of posting to the copy. If this isn't fixed quickly the compression ignition engine could start running unstoppably on the oil in its sump and could blow itself up.