OEM glass and it has a lot of little rock nicks,
.
Youtuber mentions "microscopic dirt"
in this video using Rain-X. Using 0000 Steel Wool might remove this dirt, and allow Rain-X to fill in these "pits."
"After a little time goes by, every windshield gets a little hazy. That goes double for autos that are towed right behind a large motorhome. Using our toad (towed car), we show you how to use fine steel wool, Rain-X and Invisible Glass to make your view just a little bit clearer.
Although our car's windshield has a lot of little nicks from over a decade of being towed behind our motorhome, we still want to keep it as clear as possible. Regular washing can't remove the fine dirt that gets into the pores of the glass, so we use a little detailer's trick that we learned years ago: 0000 steel wool. While you'd expect that steel wool would scratch the glass, it's exactly the opposite. Just like furniture makers use extra-fine steel wool to rub out the surface of the wood after each coat of stain, it polishes glass the same way.
NOTE: We use extra-fine 0000 steel wool in this video. It's EXTREMELY FLAMMABLE, so exercise care in storing and using it."