Yes. There are three main reasons to refinance your car:
1) To reduce your monthly repayments by securing a lower interest rate
2) To reduce your monthly repayments by increasing the term or length of your loan
2) To pay the balloon or residual on the car
Refinancing involves getting a loan to pay off your existing loan. If you have significantly improved your credit score, then you can apply with a new lender or renegotiate with your existing lender.
If you wish to refinance, check to see if there are penalties for paying off your loan early which may negate potential savings. Additionally, keep in mind that if you choose to increase the term of your loan, that you will pay additional interest.