Lets see if anyone can help me out here. I have an 08 Jeep Liberty. I bought the car in Aug and I put around 4000 miles on it. There is a total of 25000 on the Jeep. I started out getting between 17-18 miles per gallon. All of a sudden that has dropped to 13.1. The drop started with the colder weather, and I know it will (but not 5 mpg) I checked the plugs, checked the air filter. They are fine, checked the tire pressure and increased it by 2 lbs. I don't know what else to do... Does anyone have any advice for me?