I use the Mothers Back-to-Black on all the black metal surfaces (bumpers, wiper arms, etc.), and I use Griot's Garage's Non-Silicone Based Vinyl & Rubber Dressing on all other black plastic / vinyl / rubber surfaces of the vehicle -- including tires.
Here's a link:
http://www.griotsgarage.com/catalog.jsp?L1=L1_1000&L2=L2_1002&SKU=11173