example - if you pay 21k for the car - get an interest rate of 6.7% (yahoo says that is the nat. average for a 5 year loan), have 6% sales tax, put nothing down,
Your payment will be $438 a month for 60 months.
Obviously I don't know your credit rating or what your sales tax rate is where you live. Everyone is going to have a different rate. But play around with that tool and you can see how your down payment will change your monthly rate etc over the life of the loan.