If we're talking about a plastic trim product, like Mother's Back to Black...I recently got a new one by Autotech call Trim Renew.
I never had much luck with the Mother's product, as it seemed to come off in the first rain.
I have only used trim renew once, but it seems to deep-clean (the rag gets filthy) and lasts longer.
I lent it to a friend tonight to try on his brother's Wrangler on the fender flares...looked pretty good on the places we tried it...before it got dark.