MY 234K MILES M54 engine system is using coolant. Not sure how much, but I can't seem to see any leaks on the driveway. Overflow tank was very low. Checking daily now. No overheat issues with this motor ever! What should my next course of action be to figure out if its the head gasket? Or something else?
Thanks.

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X5 3.0 AUTO -2001 - 238,000 miles