Personal loans generally have a higher interest rate than a loan with colateral. I have purchased two 4-wheelers and got recreational vehicle loans that were similar interest rates to the new car rates at the time. The only possible down side with a colateral loan is that you are required to have insurance for the vehicle.
Right now, if I wer elooking to buy something like that, I would use a low interest credit card check. Got some in the mail yesterday for 3.9% until that balance is paid in full. Supposed to be for balance transfers from other credit cards, but they are checks and can be used any way you choose.