It's always worth trying to negotiate your loan repayment terms and rate.
Sometimes lenders will be more than happy to negotiate a better rate - often they'll ask what you've been offered elsewhere, and if you can give a real figure, they may be happy to quote against it.
Not all do, though - I took out a loan for a car last year, and found my personal bank was happy to offer me a lower rate, possibly because they knew they could trust me to pay it back. However, other lenders I had no history with generally looked to simply quote a general figure.