I have a 2005 pontiac wave (hatchback) it's my first car , and i've noticed it is HORRIBLE on gas I'm currently getting about 250Km/tank (45L) I don't know what's wrong with the car, it's not leaking and it runs great otherwise.... Any ideas on how to improve my gas efficiency would be awesome, or even just a reason why... Because as far as I understand I should be getting at least double that. Thanks.