[TOGWT]

Originally Posted by MuttGrunt

...Hopefully a guy like TOGWT will come in here and give the scientific break down as to how and why natural rubber breaks down, but I am confident he'll also point you towards a protection product that will help protect from the sun's radiation.

Product recommendation are correct

The seals on most vehicles are no longer made of natural rubber; vehicle manufacturers use a specialized synthetic material called ethylene propylene diene monomer (EPDM). Natural rubber, or blends containing natural rubber, just cannot endure the direct exposure to sunlight (ultraviolet light) and the harmful-to-rubber oxidizing gases in our atmosphere.

The seals around the vehicles lights (headlights, brake and indicator lights, etc) and the soft seals around doors, windows, sunroof’s, hood and trunk are constantly being flexed and compressed all the while being subjected to a hostile environment. For maintenance use a product that contains glycerine to maintain the look and feel of the material