I noticed in the engine compartment on the driver side next to the oil dip stick, there is a cap labelled "ATF Oil", I first got confused with the engine oil cap, but that is located on the top left side of the engine with a "castrol" marking. I looked at the owners handbook but there is no mention of the ATF oil cap and the information regarding the engine oil cap is very vague and of poor quality. Thanks for enlightening me on this mystery!

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August 2011 X5 3.0d