I have a 2004 jeep liberty. I recently change the brakes and now my gas mileage is dropped from 250 to 175 a tank. I have also started warming my car up for 10 to 15 minutes before I take my daughter to day care as it in extremely cold in MN. I do not smell anything or hear anything coming from my brakes. Could I just see this much of a drop in mileage from warming up my car or should I look at my brakes. If my brakes what should I look for?