what's the best way to remove the fine grayish-looking cracks on my drivers seat?

 

Unfortunately, that's a normal occurance with all leather as it wears, and the fact that it's black will show the contrasting wrinkling even moreso. If it really bugs you, about the only thing you can do is to get the wrinkles re-dyed. You could do it yourself if you have an airbrush or a spray gun & compressor, but it would require you go to an automotive paint supplier with the color code, and have them mix it. Auto parts stores sell the shaker can variety of vinyl/leather dye, but it's highly unlikey their generic black color will match your Lex. I believe Leatherique will also mix some up for you if you send them a small sample of the leather (from the underside of the seat etc.). That may be your best option.

You could ostensibly brush it on the wrinkling, and if you were careful enough, it would probably help a lot. Sorry, but those options are the best I know. Conditioners will darken the wrinkiles temporarily, but dye is the only thing that's more permanent.