The 5W-30 Castrol Synthetic you have/had for your 750 is not the same as Castrol oil for diesels. I have a Caterpillar diesel in my motor home and it requires oil specifically formulated for diesel engines. Diesel grade oils capture the sooty particles better than regular internal combustion engine oils.

Trade it or sell it (the oil), but I would not put it in my diesel engine X5, if I had one.

Good luck.

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DeanLinAZ
2011 X5 35i, Sport Activity
Black Sapphire/Oyster
M Sport, Tech & Conven packs
Premium sound, Side camera opt