Can I negotiate the interest rate at a dealership?

Often, yes. When a dealer arranges your loan, the rate they offer can include a markup above what the lender approved, which may be negotiable. Coming in with a pre-approval from a bank or credit union gives you a rate to compare against. Look at the APR and total cost, not just the payment. The CFPB (consumerfinance.gov) has guides on auto loan shopping. OffLot's Build your deal shows financing examples from sample lenders in the preview.