should i use just black or maybe rubber undercoating. my wheelwells look nasty and i think it would clean up the whole car if they were a nice deep black instead of brown.

 

why not just get a stiff brush and some car wash and clean them real good. if neccessary get some mineral sprits to get any tar off and then give it a few coats of tire shine. you'll be amazed at the difference. (not to mention that unless you get them real clean and do all sorts of prep work, paint will not last )

 

Satin black paint works wonders.

 

Undercoating would be more durable, but just don't spray it on too thick! That stuff is heavy!

 

Use undercoating. I use that all the time. In fact I just did all my wheel wells yesterday. It drys very fast. It leaves a black wrinkle look finish. Thats what they made that for.