I know this has been discussed before, but what is an easy cleaning item for the black streaks on the outside slide walls?

I find that WD-40 dissolves the streaks quickly.

Thanks

I find that WD-40 dissolves the streaks quickly.

Also removes all the wax & dirt/dust stick to it!
The factory techs recommend using Pledge furniture polish to treat the slide seals, also removes the streaks & does not attract dust/dirt.
I buy the imitation Pledge at the dollar store, saturate a rag, lift the seal & wipe down both sides of the seal at the same time. Use it on all rubber seals & gaskets throughout your RW. I've used it since we got the RW & seals all look new.

I treat the seals the same way as Danny.

For the black streaks, I find the easiest solution is driving to Indio and paying Santiagos 😆

I too use pledge on all the wipers, that knocks down the amount of streaks.. I also have a hefty coat of wax on the side walls... That allows the seals to flow across the slides with minimal binding/streaking