When cleaning vinyl, plastic, polypropylene, leather and rubber there are three points to take notice of -
1. Do NOT use products that contain Silicone, especially not oily greasy Silicone that smear on your car's paint and windows . Silicone enhances the destructive effect of UV rays and you actually grill your pannels. Eventually they will fade and/or crack. If you find no other product, chose one that is made of an emulsion of Silicone and water.
2. The number one destroyer of your pannels are UV rays from the sun, so you should use a protectant that contains a high level of UV protection.
3. Do NOT use products that contain Petroleum solvent! This is easy to find - If the product has an Explosion Hazard logo, it contains Petroleum.
When searching for a suitable protectant for my previous car's vinyl top Mazda MX5, i came across 303 protectant and have used it for 11 years. When i sold my car the top was good and nice as new.
http://www.goldeagle.com/product/303-automotive-protectant
The 303 protectant is based on an emulsion of Teflon (NOT Silicione!) and water and contains UV protection, same as used in Sunscreen lotions. I am using it on my Cactus in hot sun scorched Israel and all my black PU pannels look nice and bright as new.