The Cars Info

I know that at some point between 1994 and 2004 Mercedes-Benz went from making some of the best cars in the world to some of the worst cars in the world. I am planning on buying an old Mercedes, as they are beautiful cars (please don’t tell me that I should buy something else, that’s not what I’m asking in this question) and I would like to know exactly what year Mercedes started making poor quality cars. Please give me a specific year, so I will know that I should buy cars made before that year.