Reason I asked what parts of the interior are showing this.......my black interior panels show this as well btw, is because I first had this happening on the hard plastic panels used on my 09 Miata w/black interior.
The cause seems to be our dead skin being scraped off where we touch or rub a panel. This was noted as the weather warmed up and short sleeves became the order of the day......much less of a problem during the cooler, sweat shirt and jacket time of the year.
I found that dry microfiber towels pull it out of the grain of the plastic and pores of the cloth with no problem at all.
Note though, I said DRY.....don't put any water or other products on the toweling.
I'm guessing this type of material is some latest greatest easy to reclaim type material that has a bit more roughness than found on older cars......of course, they had less hard plastic to drag your parts against anyways.
Regardless, just wipe them down with the dry microfibre and it'll look just fine.....even the cloth seats respond favorably.
Rob
