Why do 2 same age cars,same color paint, same town, one fades, one does not?

Question

I have a Black 98 GMC Z-71. It has not been garage kept, but the paint is in great condition. I have a friend, with a black 98 GMC, not Z-71 though. His has faded, oxidized, and the clear coat chips. His was not garage kept either. Why do some cars do that and others do not. We live in the same town. I bought mine new, he bought his 2 years old.

Answer 1

probably because the material he used to wash his car and also if he left it out in the blazin' sun that might have contributed to it

Answer 2

Tell him to wax it. It might help restore the shine. Also, you might have taken better care of yours.