As you can tell by the "vin" prefix, "vintage" is derived from the wine industry. "Vintage" does not literally mean "old"; it actually means "the age of the wine". In its proper context, you would say you have a 1983 vintage Cabernet, for example.
If you want to extrapolate that to any other industry, the word "vintage" should technically be used to denote what particular age category a product belongs to. Thus, you could speak of a pre-war vintage Ford, or a 70s vintage Camaro. Using an expression like "vintage cars" is essentially meaningless, just as the phrase "vintage wine" tells you absolutely nothing.