Another major source of oil leaks on the M54 3.0 engine is the oil filter housing gasket. The gasket loses it's elasticity after several years and fails to seal the housing to the engine block allowing oil to seep out. You might want to check that also.



Here's a DIY on replacing the oil filter housing gasket.
BMW X5 E53 Oil Filter Housing Gasket Replacement 3.0 M54

If that is the problem I would recommend using a gasket made from Viton. It cost more than the stock gasket but will last much longer. You can get it here: https://www.bavauto.com/11-42-1-719855v