Could be. But the sound is more akeen to metallic spinning. Not the good kind either. More like a metallic fan with a failed bearing. The noise comes and goes. And mostly happens after the car is switched off.

I'm going to try flushing the engine next week with Liqui Moly Engine flush, followed by fresh oil filter change, and then add an additive like Liqui Moly Ceratech.

Also starting next week, whenever I drive the X5, I'm going to do a 5 minute idle before shutting it down to allow oil to flow through the turbo parts.

Hopefully that'll help with the noise.

I sure hate to have to replace one of the turbos.

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2003 X5 4.6is Estoril Blue, acquired March 2018
2013 128i M Sport 6 MT Space Grey daily driver
2010 535xi 6 MT Barbera Red