The interior must be warm for the oil to do it's job. It is a sunny day but only 56 degrees. The car is in the sun with a "heater" to warm up the interior. With the heat and the doors closed, the oil will soak in and drive out any dirt, salt, etc that is in the leather. This can take all day. Since the leather is extemely dry, the oil must be reapplied a few times until the leather is soft.