Those are cast wheels. The face of the wheel has been machined, for the most part this will close the pores of the aluminum. This keeps oxidation to a minimum. The inside spoke area is open, like a sponge.
My suggestion is to get the most aggressive cast wheel cleaner and apply it with a small
stainless steel tooth brush.
To prevent any discoloring of the machined area, coat that first with a layer of wax,
do not buff the wax off until your done scrubbing away the black dots.
The black dots are caused by cast iron dust corroding in the pores of the alloy.
I would do them off the car and rotate the tires at the same time but thats just me 🙂
EDIT: After looking at the pic again, you may just as well do the whole wheel.
The wheel cleaner I sugested is for cast wheels only. Its the stongest of about
three types.
