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Lexol is a fine product available at most farm supply stores. Most certainly adequate for the typical leather interior.
I would suggest cleaning the surfaces prior to applying any conditioner. Lexol also makes a cleaner that is easy to use.
I have found that heating the conditioner in a microwave oven for thirty seconds or so allows the conditioner to be applied easier, smoother and it soaks in better than when left at ambient temperature.
There are better products but not as easily found and are much more expensive. I sincerely believe Lexol will satisfy your desire.