FP, the discoloration seems to have been absorbed into the rubberized coating of the **** and I don't see anything about the cloth's ability to clean rubber. In fact. the list the manufacturer claims to have best effects with are all hard surfaces.

But, I think I might have found an easy and cheap cure...

I'll be needing to bring my car in for a B service and oil change very soon, and hopefully, they will once again let me use a rental XF for the day. For some reason, I think the rental will end the day with a dirtier **** than it started with.