Save the Silglyde for something it's good at, whatever that is…
When it was available,
BMW Gummi-Pflege in the tube was the bees' knees for rubber care, making it soft, pliable, and not leaving a greasy or oily residue on surfaces that might see unintended contaact.
It was interesting stuff, coming out of the tube in a thin paste consistency that would liquify upon contact, or with heat from your fingers. Apply, allow a few minutes for the carrier to flash off, and it would also avoid leaving grease trails on window glass at contact points on cars with frameless doors. That's a trait a grease like SG will not have.
Alas, it was discontinued long ago, and the 1Z product, or those like it, is the closest analog still available, in liquid instead of paste form.
303 is a protectant/sunscreen, and that's its strength, but does little to nothing in the way of conditioning, never mind having any sort of restorative properties. To be fair, none of these products do a lot in that respect, but some are better than others, and some do nothing at all.