I have around 3700 miles on my 2008 g35 sedan. Everytime I wash my car since 1200 miles I always notice a layer of dirt almost like road grime on the backend. Is there anyway this could be carbon or from the exhaust? Has anyone else experienced this?

I dont have rear mud guards and it has not been raining or does not when I check it. I do live in FL but I dont drive on dirt roads either. Just wondering is this is carbon will it go away?

You would be amazed how much dirt and dust is on even paved roads.

It's just road dust kicked up by the tires the vacuum left behind your car sucks it in behind it.

I have the mud flaps....my rear end still gets covered in carbon. Which isn't good since my car is white.

Makes sense to me, all the dust and sand we have in FL. It doesn't seem like exhaust or oil residue but I just wanted to make sure anyone else hasn't experienced this.

It's probably more noticable since I have a white car. I did'nt think about the vacuum either. I bet it doesn't help I'm always going fast so the vacuum is much sronger :-) I'm just trying to be careful when cleaning the car now so I don't get swirl marks on the topcoat.