I have scrubbed mine with a plastic scouring pad and some baking soda -- it looked better for a few months, and then got stained again due to road grime.
Thanks for the post. My wife has done a little more research since my questions and I'm leaning towards something with oil. She saw a You Tube video using Pam Cooking Spray and one using peanut butter. She's going to try one of these.