I have an ironic sense of humor.
If you listen to the commercials and the salesman, they are going to save you all kinds of money but the truth is: car salesman are trained to convince you of thatand distract you from the fact that they are in the business of fleecing the customer of the max amount of cash.
That includes the fact that you just gave them your trade-in or down payment for nothing. Talk to a salesman, off the record & they might explain how it is done.

CAVEAT EMPTOR in other words!!!