From Car Loan Wiki

Refinancing is the act of obtaining a new loan to replace your existing one. This means you will use the new loan to pay off the old one. Although there are several reasons for refinancing, the reason this is typically done is to lower your interest rate. Refinancing can also benefit you by extending the terms of the loan, paying off other debts and reduce the risk involved with a variable rate car loan by refinancing to a fixed rate car loan. If you have an auto loan with a high interest rate it's a good idea to look at refinancing your car loan. Refinancing can save you a lot of money if done properly.