I think he may have meant 1980 and older as early iron. Crinkle Zones in the frames of '80 and newer gives the early iron cars too much of an advantage
My maroon 80,000 mile ride is still maroon on the bottom side with some black components, zink looking joints and such with a rusted-up exhaust system. It is not all one color.
Anne, I would not recommend applying ANY type of oil to ANYTHING on or near your modeling area as suggested post #14. Most oils and paints do not play well together