How much more interest do I pay on a longer car loan?

Usually quite a bit more, because you pay interest on the balance for more months and longer terms often carry a higher rate. Stretching the same amount from 48 to 72 months can raise total interest by well over half, depending on the rate. The best way to see it is to compare the total of payments for each term side by side. On OffLot, the financing step in Build your deal shows payment examples from sample lenders so you can compare terms.