I worked for a car dealer in Tulsa detailing cars and we used silicone spray under the hood that makes every thing shinny and new looking for a long time. Also I had this guy detail my VW square backs wheels one time and they stayed shinny for around a month. They looked great! I went back and asked him what he uses and he told me silicone. I just don't know where to get the stuff.

Of the subject a little.
The worst cars to detail were the ones that the owners ate McDonalds in. They were always greasy and dirty with petrified French fries that never rotted or molded away (that should tell you some thing is definitely un natural) and you could never get out that MacDonald's smell, we would even pressure was the carpets!