I've noticed the same problem on my 2012 jku. A few weeks ago I was averaging the best mpg I've had so far with the jeep. 21 mpg ave. last weekend I hit an all time low of 14.9 mpg. I don't think I've ever gone below 16.9 before. If it's not the gas it could be something else. I'm keeping an eye on it then I'll check with the dealer to see if it's something more serious.