guess it depends on when you want this new car and if you have a car to use in the meantime.
first, i would make sure you would be approved for the loan. then, how much are your payments gonna be (for the whole amount)?? if thats doable for you, then it wouldnt matter if you put the money towards the loan or not. IMO, i would keep off to the side in case of emergencies.
But, you can save money on the interest if you pay it off sooner, and if you don't take out a big loan. so thats a good point too.
its really gonna depend on your money situation, and how much you NEED this money from your car or truck.
i hope this helps. i dont know which way will be best for you. each persons circumstances are different. Just do what you think is best with the suggestions.