[RMcNeal]

I have been using 3in1 RV Rubber Care Seal Conditioner.
https://www.amazon.com/dp/B07QL37GPN...v_ov_lig_dp_it
It works well. I also use WD-40 on a rag to wipe off the black streaks and residue. It's amazing how well that works. No hard rubbing, it just wipes off. Easy Peasy.