I have (had) black bumpers on my car, with time they are slowly becoming grey.
They are made of some kind of softened plastic I would rate between regular plastic and rubber.
Is there a product I can use to restore them ? I don't want to paint them since I'm sure it won't hold. I tried Armor All, it does a nice job but it lasts 2 days.
Have you tried Vinyl dye? Only other thing I can think of that might work is water based paints that hold very well (black High heath BBQ paint is one) but I'ld try the dye first.