I actually know the perfect answer to this question, however you may not like the answer.
A good friend of mine told me shortly after I purchased my WRX and started complaining about the gas mileage, that if I couldn't afford to put gas in the gas, I shouldn't have bought it. Period.
You knew this when you bought the car. You stood there with the sticker right in your face. you bought a performance car and you're going to get performance car mileage. Deal with it, or trade it in.