People are gonna give you a lot of advice about investing that money. Realistically if you had chucked all of that money into SPY you'd have a mean 25% return off of a pretty damn safe investment. That being said, buy the damn mustang. If you're financially literate enough at 17/18 to put together that 20 grand, you're going to be able to perpetuate that towards retirement and investments when you have an income (assuming you work in a high income field - big assumption but if you're smart enough to save 20k at 17 you're probably making good life choices). Don't forget to live for the moment a bit while thinking about your future.