I got a question a week ago that I thought would make a good post, so here it is! Someone asked that their leather jacket always seems to get mildew on it. They said the jacket always seems to have oil on it, no matter how much they hang it up to dry. They wanted to know how to stop it from getting mildew.
Well, it sounds like the leather jacket has too much conditioner on it. Or, the type of conditioner on it is thick and heavy and not the right type to use. Leather conditioner is nothing more than oil that you rub into your leather item. Some of them have several different ingredients mixed together.
The whole point of leather conditioner is to make the leather soft and prevent it from cracking. It also acts to make it water resistant. The oil protects the leather fibers, replacing the natural oils that were there when the animal was alive. However leather also has to breath and let moisture out.