No amount of Armor All can keep your new car from losing a chunk of its value the moment you drive it off the lot. And if you purchased the car with a loan, you just increased your chances of having an upside-down car loan. So, if you’re the lucky owner of an upside-down car loan, don’t worry. We’re here to help. If you owe a small amount (for instance $2,000) on your trade-in, your car salesman will pay off your old loan and pay you the difference ($1,000), minus processing fees, etc. You might also have to pay state sales tax on the entire purchase price of the vehicle you are getting, depending on what state you live in.