Your grandparents purchased a car for you in their name and you are wanting to refinance the car in your name How do you go about doing that?

If the car is in their name and they want you to take over payments then they need to sell it to you. There is only so much you can do with refinancing. In this matter, unless they are cool with keeping their name on the title with yours, then they must sell it to you. That means you need to secure a loan for the purchase of your "new" car.