If the car is relatively new, it could just be from the outgassing of the plastics. Basically when the plastic is made, there are chemicals that get trapped inside of the plastics. As the car gets hot from sun through the windsheild, the pores open up and slowly release the gases. This is what gives you the "new car smell". This is completely normal. When I first cleaned my car, there was black crap all over my microfiber cloth from the outgassing. It will also cake on your windsheild as well.
You could dilute some APC, as APC might be a little strong on its own. I see someone mentioned 10:1 and then 5:1 if it isn't strong enough. I recommend this. Just do not let it sit there and dry. Get the crap off and then get back in and clean the APC off with a damp cloth and then use whatever protectant you use on the dash.