Grease stains on side of car under door

We have had a 2007 Camry & now a 2007 BMW, both of which get grease stains on the area under both front doors. It is not on the door or anywhere else. Just in the 6 inch or so high area under each front door (both sides, 6 inch by 24 inch area). We also have a Saturn Vue but it does not get them. We can clean it off with Goo-Gone or Dissolve-It, but it still requires hard scrubbing. The car is Silver so the black stains are very obvious.

What is causing it?

The BMW dealer said it was some kind of wax they coat things with during manufacture that oozes out of the door, but after 5 years that should be gone. Just frustrating since it so quickly re-accumulates after cleaning.
Jim Gabler

They do use a rust preventative wax…um, perhaps the Saturn doesn’t have any…but the only way to really tell where it’s originating from is to pull the inner door panels.