Good info about Simple Green and the 3M product. I had better stick to Simple Green or mild soap and warm water.
It may just be that the new car with word "MINE" scrawled across the hood has been scratched as opposed to stained.
I had a car for years with a big matte black decal on the hood. It was high maintenance and always had something going on.
Bird crap, water spots, finger prints, wax, biker chick rode on the hood and left something on it.
Some stuff came off over time. Other stuff stuck around like battle scars.