Believe it or not, the stock leather seat skins are coated with vinyl to make them last longer and to protect them. Therefore it is kind of tricky on what to apply to them to protect the leather and the vinyl. Use the wrong thing, and it will break down the vinyl coating into a gooey mess. Also, the seats are still half leather and half vinyl. Matter of fact, nothing on the rear seats are leather. On the fronts, only the part your butt and back touch are leather, all else is vinyl.
That being said, and not wanting to use two products on the same seats, I use Eagle One Nano-Protectant.
Copy and paste ad:
One-step cleaning and conditioning for both vinyl and leather
A car that looks its best helps you feel your best when you get behind the wheel. Now you can go from your dash to your leather seats in one easy step! Treat your car right with Eagle One Nano-Protectant. Our formula is long-lasting and enhances surface penetration by using tiny nano-sized particles for optimal cleaning, conditioning and UV protection of both vinyl and leather. And, the trigger applicator allows for controlled application.
Dries quickly to a smooth, natural-looking satin finish with no sticky residue
Penetrates deep into surface for long-lasting results
Excellent UV protection helps protect your interior from damaging rays
Clear formula provides clean, streak-free coverage
If you want something shiny and slick, this is not for you. It is bone dry after a few minutes.
So what is the bad news? It doesn't smell all the great, closest thing to urine I've ever smelled in a car cleaner, but I can cover that up with some air freshener (Febreeze Auto).