In order to remove the decking oil on the panel, I suggest using Intergrain 1L UltraPrep Tannin And Oil Remover. It's used to lift old or weathered existing timber finishes and prepare timber for coating. It can also be used as a high strength cleaner. On new timber, it removes dirt, tannins, natural oils and other contaminants from the timber surface, preparing timber for coating. Please note that you'll need to apply several applications if the oil is deeply embedded in the timber.