Refinance your car, get $300. That's the deal for members of Grow Financial Credit Union who refinance their auto loan now through Aug. 31. The Tampa-based credit union has refinancing rates starting at 2.99 percent APR. The bonus gets deposited into a member's saving account when the loan closes. Grow Financial has 18 branches and serves more than 156,000 members in its five-county Tampa Bay market.