The care and feeding of the leather and the vinyl components of your BMW 2002 interior are two very different processes. If you are using one product on both, that is somewhat like using gasoline as a lubricant. It will work, but not for long. I will cover the care and feeding of leather and vinyl separately.
Leather, having once been used to keep the insides of a cow from falling out, is designed to pass moisture through tiny pores. These tiny pores absorb human perspiration and as the water evaporates, salts contained therein remain to absorb the essential oils in the leather. This accumulation of salts and other grunge should be cleaned from the leather about twice a year (more often if the seats get more than their fair share of your leftover sweat). The loss of oils within the leather is the first step to hardening, cracking and shrinkage.
Leather dashes are very prone to hardening and shrinking. Your dash is subjected to the destructive UV rays and heat concentrated by the windshield. The leather (or vinyl) of your dash rests upon a metal backing that acts like a frying pan. This "frying" drives the essential oils from the leather causing premature shrinkage, cracking and hardening. Thus a dash should be treated more often than the seats or door panels.
Cleaning leather may be accomplished by using a mild soap and water, or specifically designed leather cleaner. Of all the products I have tried, I still like Lexol pH Cleaner. It is pH balanced, and gentle. All cleaners will re-hydrate the leftover salts and grime and wash them from the leather fibers.
Use only leather products on leather, do not use vinyl cleaners as these products tend to be much harsher and may not be that beneficial to the leather.
Any cleaner should be rinsed thoroughly from the leather. I have tried spraying off with a hose, but that just seemed to fill the car with soapy water (a hole drilled in the floor was needed to drain it out - just kidding). I went back to using a damp cloth and repeatedly wiping down the leather. Once the leather is clean, a conditioner should be used to restore lost oils and emollients. There are several conditioners on the market. Two of my favorites over the years are Lexol Conditioner and Tony Nancy Leather Conditioner. These two seem to be the most easily absorbed into the leather fibers and tend to leave a relatively less "greasy" finish than any of the other products I have tried. Another good product is Connoly Hide Food. This product is made from rendered animal parts and will turn rancid in about two years. This and the distinctive "cow" smell removes it from my top two list (I spent too much time milking the south end of a north pointing cow, so am not a fan of cow smells). Zymol makes a product called "Leather Treat". It does not, in my humble opinion, do any better job than the much less expensive Lexol or Tony Nancy products. Again, do not use a vinyl product as a conditioner on leather and above all try to avoid silicone based products. The silicone oil will dissolve out the leather's natural oils and tend to make the leather sticky. Silicone has a very high electrostatic attraction, and will invite every dust particle within miles to set up camp in your interior. Apply the conditioner to a soft cloth and work into the leather, allow it to be absorbed into the fibers and then buff off the excess. You may condition the leather will tell you if you apply too much or apply to often. The leather fibers will just not absorb the excess.
If your leather has hardened or needs some intensive softening, there is a really nifty product called "Surflex Leather Softener: This product is made from natural and synthetic oils that restore the natural softness to neglected leather. Clean the leather and then apply a liberal coat of soffener. Allow to penetrate the leather for about 24 hours. Wipe off the excess. If it needs an additional application, repeat the above. For really bad areas, cover with plastic and allow to sit for a few days. Once the leather is sufficiently softened, allow to "cure" for another 24 hours and buff off any excess. You are done. I jokingly say this product will turn a dog's rawhide chew into a kid's glove. I have had some luck with leather dashes with this method. Once the leather softened, I have been able to gently tuck it back under the edges of the trim and windshield clips. This is a lot cheaper than a new dash and may be worth a try before spending a ton of money.
Author: Larry Reynolds