I've used a few treatments, some good, some not. Mothers Back to Black works but doesn't seem to last very long, and sometimes needs a couple of applications to get a solid color.
This stuff, Forever Black, not only works but seems to last for a long time. I used it on the panel under the wipers and it has stayed black for a few years. It also needed a couple of applications to look good
I've just used this stuff, Black Jack, and it really worked well on the convertible top arches and the plastic bits down in front of the wheels. I've just tried it for the first time so I don't know hown long it will last, but it is really easy to apply and really brings the black color back. Unlike the other treatments, I was able to get a solid color with one application.
There ya go, Felix!