I'd have to agree, that if your cobra is in good mechanical condition to keep driving for a while, keep it! The average driver puts around 12k miles per year on their car. If you are getting 20mpg in your mustang (I average at least that in my driving), then switch to an econo-box that gets 26mpg average, then you are saving less than 30$ per month. That's nothing compared to what you probably spend on your cell phone, alcohol, food ect. Do an actual cost analysis to see what you would save first, because I seriously doubt it will be that much. Especially after you pay taxes and tags on the new car.