Tip #1 for negotiating a better price from a dealer: Under no circumstances should you ever leave a deposit before you've agreed on a price. Refundable or not, you need to be completely and utterly detached from the car in question to successfully negotiate. Walking away must be the most likely outcome unless the price you want to pay has been met.
Psychologically to both parties, you have made a commitment to that vehicle by leaving a deposit - even though it is refundable. You've put skin in the game, you're already on the back foot.
Psychologically to both parties, you have made a commitment to that vehicle by leaving a deposit - even though it is refundable. You've put skin in the game, you're already on the back foot.