[gw84]

I've not found any products that work great for this purpose. One product that I have used is "Turtle Wax wet n black." The label says that it "...provides the ultimate deep black, wet look for your tires, black rubber bumpers, and black vinyl trim...." It made the surfaces look good (and black as the label promised!) but I don't think it would do much for "preserving."
Before I found this product, I had used Armor All and other similar products to try to preserve my trim.....mistake!! Sure, it made them look good at the time, but over time it actually seemed to dry them out. OVer time they began to fade and become brittle.

Because I was having no luck with products, I went to the junkyard in search of replacement trim. To my surprise, there were actually several vehicles that had better looking trim than mine (it's a '93). I got a few pieces for a couple of bucks; and a couple years later they look good as ever. NO PRODUCTS used!! I just swapped them out. I haven't checked, but I'm sure you can buy them new and then wouldn't have to worry about them for many years to come. You can experiment with some different "conditioners" and such, but stay away from the "protectants" such as armor all, they will just dry them out more.