Ihave an 1995 Impreza L 2wd and for some reason I am getting barley any miles to the gallon. I have jsut receantly gotten a Fuel Filter and a O2 sensor on it. I know its not leaking gas becasue i have gotten it checked up. the fuel tank on the car is 13.2 gallons and is supposed to get around 20 miles to the gallon what is happening?