I use the Mothers leather cleaner, followed by their conditioner, has worked pretty well for me.

My father swears by saddle soap, started using it in all his Corvettes back in the 60's and on everything since. Haven't had a chance to try it yet, but if it can protect a horse saddle, which is exposed to direct sun, dust, dirt and grime, then it should do wonders for car seats.

Best stuff I've ever used (and still use) is a product called saddle soap.
You can get it from any tack shop or equestrian supply shop.
It goes on as a paste, is clear, and moisturizes and protects your leather.
You need to apply it @ 4 times a year.
--
'94 850 154000kms '86 760GLE 272000kms

P.E.

I've used Leatherique Rejuvenator Oil and Prestine Clean with good results.

Some cracking and loss of color is inevitable because of the way the leather is dyed. If it's bad they make a crack filler and custom dye that is fairly easy for the DIYer to do.

With either product the key is regular maintenance.

Bryan