@Robert M -- thanks for the shout out.
For oxidized rubber, I haven't seen anything better than Adam's Tire and rubber cleaner. It will take white, old looking rubber and make it a deep, rich black. After that, I like to use Adam's VRT -- this keeps it black, but it is not a glossy black that attracts dust. The rubber just looks new.
Will, let me know if you're ever passing through Fresno. I'd be happy to give you some of both. I have all of this stuff in 1/2 gallon containers.
Regards,
Anand