Before you refinance the car
Four numbers, and one of them tells you whether the other three matter.
Refinancing an auto loan is one of the few money moves that is genuinely simple and genuinely underused. You are not selling the car or changing anything about it. A different lender pays off the old loan and you make payments to them instead, at a different rate.
The four numbers
Your payoff amount. Not your balance on the statement — the payoff, which the current lender will quote you, good for a set number of days.
Your current rate, as an APR. It is on the original contract. A surprising number of people financed at a dealership and have never looked at it.
Your remaining term. How many payments are left.
Total remaining interest. Take the payment, multiply by the payments remaining, subtract the payoff. That is what the current loan will still cost you. It is the number that decides everything.
Why the fourth number decides it
Auto loans front-load interest. Early in the loan, most of each payment is interest, and there is a lot of interest left to save. Late in the loan, most of each payment is principal, and refinancing rearranges almost nothing while costing you the effort and a fresh credit inquiry.
If your total remaining interest is small, stop. It does not matter how attractive the new rate is — you cannot save much of a number that is already small.
The trap
A lower monthly payment is not the same as a cheaper loan. Stretch a loan with three years left into a new five-year term at a better rate and your payment drops noticeably while your total cost may go up. That is a legitimate choice if your problem is monthly cash flow this year. It is a bad surprise if you thought you were saving money.
Insist on comparing total-to-total, not payment-to-payment. Any lender who resists that comparison has answered your question.
When it will not work
If the car is worth meaningfully less than you owe, most lenders will not refinance the gap. If the vehicle is old or high-mileage, options narrow. And if your credit has gotten worse rather than better since you signed, the new rate may not beat the old one.
Bring the payoff and the contract into a branch and someone will run it honestly, including telling you not to bother.