The o-ring can be replaced every time the filter is changed as the filter comes with a new one. I use a tiny amount of fresh oil on the o-ring also.

Overtightening can crack the plastic lid. I think they have a torque spec but in both my M5 and the X5d, they just stop turning.

__________________
8/2011 X5 xDrive35d Sport, Black Sapphire Metallic, Black Nevada Leather, Fine Burr Walnut Trim
2/2001 M5, Jet Black, Exclusive Complete Black Walk Nappa Point Heritage Leather, Black Cubic Trim