ColoML550

So my employee today said to me that's the most dirty she'd ever seen my car. I did wash her on Sunday - then it snowed that night. Ug!

Anyways she asked me what the lines on the door were. I had no idea. Any ideas? I told her its the difference in metals. It's the exact same on the passenger side.

350MH83

I was asking the same question when I saw your first pics a couple of weeks ago... Now the more I look at it, the more I think it comes from the fact that those are the spots where the door external panel has a mechanical contact with the inside stuff. Those spots are warmer when you drive and this means that in sub-zero temperatures, those spots are the only one not to be frozen. Hence the mud sticks more easily on the rest, as it freezes.

Taymar16

That is where the door reinforcements are located. The lines are a material that is added between the reinforcement and door skin that has several functions. It prevents the door from vibrating and having a drumming effect during closing and driving down the road. It also asks as a support between the two as well. It looks like black tar foam. Good picture!