Dirty Volvo Wheels

I am confused as to why our new Volvo S60's wheels get so dirty so quickly. The front wheels are the worst but the rear wheels get covered in the same oily black residue. It also sprays on to the sides of the car too. We have other non volvo cars and they do not have this problem. I have been checking out other cars and notice that Volvos have really dirty wheels! What is happening?

Maybe residue from the brakes?

i think the roads you are traveling are dirty if not as blue said residue is another reason