From the
Lexol web site: "Vinylex Protectant cleans and protects with a patented, one-step formula that actually nourishes vinyl, rubber and plastic surfaces. It actually penetrates below the surface layer to nourish and revitalize underlying plasticizers, thereby reducing cracking."
It is expensive, at about $9 a bottle, but it does work very well. It worked wonders on the seat and door panels I got from the junkyard. For cleaning stubborn stains, I found the product to work best with a scrub brush. Wipe with a paper towel, then follow with another application.
If you spray on a heavy application and let it soak, then yes I think it will help soften the material.