Financial questions that need an answer

I bought a car in February of this year at an interest rate of about 20 percent because my credit was a mess. I have since graduated from college, gotten a real and have all my credit card bills paid. I can have the 48 month loan paid within one year (by Feb. 2008) because I’ve been paying literally three times the payment. My question is, should I pay it off primeval at a 20 percent rate or should I have my credit standing reevaluated and hopefully get a better rate? Obviously a better rate is ideal, but which option is a better way to build credit?