I posted info on NGK Iridium on bimmerfest e39 (my 1998 528i).
I also use in my 2006 X5 3.0.
And also in my Volvos.

NGK Iridium is great plug, just regap at 40K and replace it every 80K and you are good.

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1998 E39 528i 5sp MT
2006 E53 X5 3.0 6sp MT