I've gotten offers from Cap One and most recently HSBC to refinance my car loan (that I took out last August). They all said I "could" qualify for rates "as low as....." 7-8% if I had excellent credit, yada yada... However my original loan thru Honda Finance is only at 8% (and this was gotten 3 yrs after bankruptcy). So I will never refinance because I know I would end up getting a higher rate than I currently have and will have wasted inquiries on my credit report(s). Besides I have been paying over my due amounts each month (usually $50 more) and now just over a yr of payments, my amount due each month has almost been reduced by 50%!. So now I am sending in double payments each month, plus another $10 extra.
But if you have excellent credit with no public records, baddies, lates, etc...then definitely shop around for a better lender. I also keep reading that credit unions seem the best way to go.