Getting shine back in black plastic

Lemon Pledge does a quick job of it but it doesn't hold up too long. That's what the dealer where I bought my first tractor used to brighten them up.

A couple times I have used the same Si02 product that I use on the boat and it does a good job of protecting or at least beading water for a while. It has to be shiny to start with and the ceramic coating will help keep it that way. But to tell you the truth I'm not the most ambitious feller when it come to shining the tractor so the easy to apply stuff is always my choice. I have a black car and that seems to use up all the enthusiasm I have for polishing.

OOps, I didn't read the thread title close enough and missed the question being about the black plastic. I don't have any specific suggestions for that, but thanks for all the good tips here so far.