Black permatex. For the best results, finger tight, 1/3rd final torque, 1/2 final torque, let sit for a min of 12 hours, then final torque. This allows the permatex to "setup" in the filled gaps and makes a better final seal.

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'03 X5 4.4 Sport, last of the M62s (8-03 build date)
I believe in deadication to craftmanship in a world of mediocrity!