You are not in the best position here unless you can prove a contract or agreement between you and your Grandmother regarding the vehicle.  Just because an agreement is not in writing but rather made orally does not mean that it is not valid.  In other words, you just have to prove the elements of a contract were met and that you have been living up to your end of the bargain.  I would speak with someone in your area on the matter.  There can be certain pitfalls to oral agreements that are part of the local law. It is better than having the car you have paid for being taken from you without a fight.  Good luck to you.