after i wash my car i drive it around and the car is still clean but the trunk is not white is is semi black, dirty with what i think is oil but im not sure.

 

Is the car running funny at all?
Could be oil or Carbon from running rich.

 

Rear main seal?

 

Possible.
If you have a turbo could also be a turbo return line o-ring bad. (Forgive me for not being able to remember if you have a turbo or not)

Clean good from underneath if the bottom has oil on it and test drive and check again.

 

the car runs fine...it could be the turbo seal....