Seems rather contradictory, but . . . my "ebony" Generation 1 side cases have FADED! (How can black fade?) Their color, now, is more-or-less grey-green.
I've tried numerous cleaners/polishers/etc., but . . . no help!
Full disclosure: I've NOT tried motor oil. Even if the oil makes 'em shine, not much improvement over the ghastly color. And . . . I'd think the oil a very short-lived expedient.
Again, good luck and I hope solution is found and shared.
“You better put down that gun. You got two ways to go, put it down or use it. Even if you tie me, you’re gonna be dead.” "John Russell" (Paul Newman), Hombre