If you have a car loan out and decide to pay the car loan off earlier than the full loan term then yes your credit rating and credit score should increase by at least 10 to 50 points depending on the credit report that was made.
However it's better to keep the car loan for the full term to show that you're even better at paying loans back because the longer you have the loan open it helps you to build a payment and credit history overtime and will increase your credit score much more overtime than just paying off your car loan early.
But yes you can pay off your car loan early and maybe have to pay an early loan payoff fee and your credit score should increase at least some.