Similar problem here. I lost 5-6mpg since the shifter recall was done this past Summer on my 2014 GC. My mileage has drop to as low as 16.5mpg in Dec and I have not been able to get >20mpg. Right now it's seems to get roughly 19mpg most times. I've been back and forth to the dear several times for this and other issues. I have an open case with Jeep on numerous issues and as of yesterday the feedback on the star case was that nothing is wrong since it seems that I've got the update that will apply to the 2017's. They said the 2017's will be rated at 15mpg city and 25mpg highway.Not to be a conspiracy minded but before this announcement I went in for a 36K service and they "bricked" (their term not mine) my PCM during a "routine OTA (over the air) update" and the Jeep dealer had to replace the entire module. The service manager stated "...i have never seen this happen before..". My understanding is this module contains firmware related to emissions. I noticed that my mileage went down +15% (29 hwy --> 24 hwy) and my range decreased but didn't connect anything until after the announcements. if this is related the "fix" looks like it has a significant negative effects on mileage.
Feedback of any similar experience is appreciated
Needless to say I'm furious and feel that I've been deceived. This Jeep has been a disaster for me. It's has had so many problems and I only have 29K on it. Nothing like my 2002 Jeep Liberty where nothing broke for the first 90K and that my daughter is still driving at 180K. I don't think this 2014 will last 50K.