Clean OEM running boards
Long story short: the winner was Barkeeper's Friend, a dish brush, and one of those dish washing sponges that has a plastic abrasive side to it. Wet the running board and sprinkle Barkeeper's Friend along it, maybe a teaspoon's worth every 12-inches or so. Use too little rather than too much; you can always go back and use more later. Wet the brush and gently work the powder into a lather around each rubber insert. Use the abrasive side of the sponge -- don't use steel wool! -- to rub off all the marks and corrosion. Leave each section alone as you move on to the next one; Barkeeper's Friend is oxalic acid and it will gently continue to clean if you leave it alone. When you are finished one running board, hose it clean using a generous amount of water. You don't want to leave any dried oxalic acid in there. Dry it with a soft cloth. The result is amazing. Time for both running boards (after I had spent who knows how long trying things that didn't work): about 30 minutes.
Barkeeper's Friend is not just oxalic acid, it also contains a very mild abrasive which helps to lift stains. If you have sensitive skin you should probably use plastic gloves when handling it. You can buy it at many hardware stores and kitchen stores. And no, I don't have shares in whoever makes it!



