For cleaning, the best thing you can do is use a very soft clean towel slightly moistened with water. Chemicals are very hard on plasticizers in vinyl. If that doesn't clean your dash, your car is way too dirty, but any leather cleaner like Zaino's or Lexol's is usually mild enough to use. Here are the best products available for conditioning plastic/vinyl in order:
1. Zaino Z-10 "Leather in a bottle"
2. Formula 303 Aerospace protectant
3. Lexol Vinylex
The top 2 leave a dry satin finish whereas Vinylex tends to be a little more oily and glossy. The first 2 contain SPF 40 and all of them contain some UV protectants. Zaino is actually a thin cream and comes out on top because it smells the best (It smells like real leather

) and lasts forever, like all his other products.
...All in my humble opinion of course....