i havent been able to wash my car in the past few weeks becuase its been cold and rainy. i noticed i had that smokey exhaust film on the rear of my car. it washed off pretty easy.

my question is- is this film harmful to the paint in the long run?

and what causes this? i recently got a new DP and midhoghflow.

 

Nah, just keep it clean and maybe put a couple of layers of wax on there to keep it from accumulating. You're probably getting most of it during cold starts and idling since your pre-cat helped to clean things up on start up before the dp. Once you've warmed up you should be tree-hugger friendly.

The best way to warm your engine is to drive right away-gently for about 15 minutes.

 

drive it? i usually sit for about five minutes or so. what rpm should i keep it under?

thanks for the advice on the wax, i was thinking that would help.