It depends on a few different criteria. The main thing to looka t is how much you owe on it and how much longer it will take to pay off. Also, look at the difference in the final amount you'll pay and find out if your current loan requires a fee to transfer (early payoff fee).
I recently refinanced my car because I switched banks and got an offer at 5% lower than my originaly loan. It freed up about $75 a month and lowered my final total by about $1k. My old lender did not require any fee for transfer either.
One hidden fee I ran into is that you may need to have your title changed, which can cost up to $100 in some states.
Basically, take the time to do the math before taking any official steps.