And how do I get this off!
We purchased a car for my son. A chevy malibu. It has the original hubcaps on them. It is hard for me to tell if they are plastic or metal.
On all four hubcaps there is like this spread/spray of orangish somewhat crusty but imbedded into the hubcap. It is not crusty enough to just scrape right off. Upon closer observance I can scrape with a plastic card a very, very thin film of what looks like clear plastic on the hubcaps. If I could remove this film then the orangish stuff would be gone. But it is all so imbedded and very hard to remove with the plastic card, only getting a very tiny chip of it off.
I probably need to use something more rough. I've only used a general cleaning brush (large), some home cleaners, and I've tried using a toothbrush... does nothing... it's too smooth. I am able to chip some thicker pieces of the orangish stuff with my fingernail, but there aren't many thicker pieces for me to do the whole thing and that would take forever anyway!
I thought it was rust, but I don't think so anymore. It looks like some type of dried up grease maybe?
I would love to get new rims for it, but that's going to be a while.
I know the car would look SO much better if I could clean these hubcaps up... it's a nice car.
So what in the world is it and how do I get it off?

The best way to describe the look of this is as if someone put some syrup in a spray bottle and sprayed a thin layer of it on the hubcaps that dried up and got stuck... forever lol.

Sand it down with 320 grit, spray it with plastic bumper paint.

You didn't say what year this car is. If it's not a classic, you could try buying new hubcaps. I just looked on eBay and there are plenty of choices right there.