I noticed the same thing when I bought my '04 XF a little over a month ago. I did try some 409 to try to clean it off with no luck. Maybe it's not "dirt" but some kind of reaction of the "rubber coating" on the **** with the natural oils on our fingers. At this point I've decided not to worry about it. Now if it's easy to get new **** and it doesn't cost a lot of $$$, I will replace it.