frmach
When I bought my Z3 I bought the best wax (almost) I could find/afford.
It is Carnauba based wax (72% I think), the theory is that the oils keep the paint hydrated, it is a pain to apply it Has to be done by bare hand but LOOKS AWESOME, I used it on my Smart last summer (TOOK THE ENTIRE DAY TO WAX AND BUFF), but here are the results
http://www.putfile.com/pic/6319224 as can be seen the sun and the tree line are reflected on the paint.
Today when I wash it (and towel dry) THE SINE IS THE SAME.
Hope it helped
ASM