You should read "The Millionaire Next Door." (http://www.thomasjstanley.com/pub-books/1/The_Millionaire_Ne...) There is whole chapter on why you don't buy new cars. Mostly because they lose a ton of value as soon as you drive them off the lot.

Most millionaires in the US drive American-made cars that are 2 - 5 years old.

EDIT: It's actually not "most millionaires" -- only 20%: http://www.thomasjstanley.com/blog-articles/395/Millionaire_...