The CU rates are good for someone with your credit rating. I would call the dealership and ask what their rate tier breakdown is by score or ask what you need to qualify for the promo rate. If they take a 680 bring in a copy of your EX and/or EQ and go from there.
No other lender is likely to offer you a much better rate than your CU unless a dealer is running a promotion. A private lender would not touch that rate on a used auto loan for a sub-A credit rating.
