I am a 17 year old who got this car as a hand me down from my step-dad and when i got it i noticed that the mileage said 10.4 mpg which i already thought was unusual but slowly but sure the mileage has been dropping. I have not been driving crazy been driving the same way i have been since i got it 5 months ago and now the mileage is 9.8 mpg. Is there anything i can do?