The advantage is purely cosmetic. It can actually lessen the life of the tire by breaking down the oils on the surface. I use "tire wax" sometimes because it looks nice and I haven't had any problems with tire degredation - it's more in theory. The difference may be seen over a number of years.

 

Dexter,

What is "tire wax"? Where do you get it? and.... Who makes it? Thanks!!

 

It's kind of a thick goop that you rub on the tires and then use a brush or a rag to spread it around. I think it's made by Turtle Wax. It tends to last longer than the normal stuff and it's easier to keep off your wheels. I get it at K-Mart.