On the driver side of my car the plastic that sits on the floor next to the seat is filled with black scuff marks. I tried an APC and a toothbrush but no good. I guess it's from my shoes, any help would be appreciated.
It could be vinyl or plastic. There are a several products that are designed to clean plastic and vinyl. If it's plastic, use a plastic polish. If it's vinyl, then use a vinyl cleaner.
I agree with John completely - use Mr Clean. It works extremely well. I just used it again tonight. A few swipes of the sponge and "poof", black marks are gone.
Try a Lowes, Home Depot or Fred Meyer if you have them in your area. Get a 4-pack. Much cheaper per sponge than the 2-pack.
I simply use a small amount of Stoners Tarminator sprayed onto a cloth. The solvent in the product disolves the scuff marks and so far it appears to be safe for vinyl. Of course, I always wipe the area clean after the marks are removed and apply a vinyl protectant.