My car suddenly started using gas. I thought it was the air conditioner being on

Do you see any signs of black smoke from the exhaust or any smell of raw gas. Is there a Check Engine/ Service Engine Soon light on? If a light is on codes stored in the computer may indicate where the problem is. I would need to see scan tool information to see the O2 sensors are working correctly, that the ignition and fuel system are working correctly and the computer in your car is determined that the correct amount of air is judged to have entered the Engine.Autozone have some popular workshop manuals for free on line once you register (for free) on their website http://bit.ly/autozone_repair_info. There is a company that independent auto repair shops get their information from, this same information is available inexpensively for people that work on their own cars.. The information is year make and model specific, covering repair procedures, torque specifications, fluid capacities and specifications, service bulletins, component locations, wiring diagrams ect.... Alldata is very easy to navigate http://bit.ly/AllData_Repair_Manuals_Online