O.K., so you don't like you car anymore. I hope you do reconsider, because any and all cars will require maintenance over time. You're in Dallas where you are close to a dealer and most of the parts, excluding engine and transmission, are going to be the same as a regular Mazda 3. And it will take you a loooooong time to recoup your depreciation loss on sale or trade and the difference in gas mileage.
My other vehicle is a huge, thirsty Nissan Armada with four wheel drive and a towing package. Think 10-11 mph around town and maybe 14-15 on the highway. My car gets about twice the mileage, but the math is not really in favor of chosing the better mileage.
Example: If my Armada gets a crappy 10 mpg around town and I put 10,000 miles per year on it at $3.50 per gallon, that's 1000 gallons at $3.50 or $3,500 in fuel.
If my Speed 3 were to only get 20 mpg around town (I do a bit better), that would be half that or 500 gallons at $3.50 or $1.750 in cost and $1,750 in annual fuel savings.
Think about how many years it would take at $1,750 per year to pay for the difference in trade in on your present car and the cost of a new one, including tax and insurance. And at that point, many, many years down the road, you will have just broken even!
And I doubt you would have as much of a difference in fuel cost as in my two examples. You might only save half of that every year. And add on top of it that you will probably be financing your new purchase and have to add the interest cost on a new loan when your present car is probably paid off or well on its way. If not paid off, then you've got that additional payout to probably refinance.
But, if you just don't like your car anymore, get something you do like. I would not hold my breath expecting to come out in a better place financially, however.
