How can I tell if my car needs an iron remover?

Visible orange specks, persistent roughness after washing, and heavy brake or industrial exposure are common signs. On dark cars, spraying a small area and watching for the color reaction is the easiest check. An iron remover is most useful when ferrous particles are present; it should not be used simply because the paint feels dirty if another type of contamination, such as tar or overspray, is more likely.