N52 engines are notoriously loud. Engine oil will usually look dirty even right after being changed.

That being said, I highly recommend getting a “used oil analysis” performed when you drain the oil tomorrow. Save some used oil in a clean jar or plastic container and order an oil analysis kit (I have used Blackstone a couple times). That is the only way to k ow what is going on inside the engine. I believe they are $20-25.

Also... are you using Castrol Edge 5W-30 A3/B4 or regular Castrol Edge 5W-30? The latter is not suitable for BMW engines.

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2007 E70 4.8i