replaced mine couple months back with a silicone one. noticed that it's covered in oil today.
took it off to check for splits, but it's all good. maybe i didn't tighten it as much as i thought, but i'm not sure.
took the car for a drive, coincidentally, drives better than it should. no lumpy idle, no stalling when pulling off.
is there any other reason why it's covered in oil? and do the symptons have any connection?