If not an oil issue, but one of wood color, here's another one, but only if really necessary.

Oxalic Acid could be an option as well. It's wood bleach. "Wood Brightner" or "Deck Brighter" contain it. If you go that route, a complete restain may be necessary.

Apply it hot, allow to dry around five minutes, then reapply. More coats if necessary. After allowing to dry thoroughly, rinse well with water. Allow to completely dry.

Regards
Ken

Last edited by Ken61; 01/07/17 08:00 PM.