A used car can look beautifully repaired and still leave one important question unanswered: who supplied the parts used to fix it? That question matters most after a crash, when a vehicle may have received replacement components that affect occupant protection, visibility, or the way the car handles another collision.
Aftermarket parts are not automatically bad, and federal rules do not generally prohibit their use in repairs on used vehicles. NHTSA says aftermarket parts can be used as long as a repair business does not knowingly disable a required safety system. Some replacement equipment, including lamps, brake hoses, windows, windshields, and seat-belt assemblies, also falls under federal safety standards.
