Dollar store vaseline! Believe me there is nothing better to absorb in, & preserve the black trim then this, because of it's semi-solid average temperature consistency, It lasts forever. It may take a while to sink in, and require occasional excess removal, but once this is done, it is better then anything I've ever used! It can also be used on tires.
I've used it a lot on faded, powdery, fibreglass boats with great results. The color, & gloss, comes back like new, and when totally absorbed, & dry, wax, or polish as usual, for even better color, & shine!
Check this thread, it's exactly like I said supposedly in the owners manual "a light coat of petroleum jelly for exterior trim protection" I haven't looked yet so I can't confirm? but I'm a believer, used it on my cars, boats, jet ski's & motocycles