mud hole removal here...haven't cared enough to check MPG but doesn't seem much different.

 

Jeep refers to it as an "Air Dam", and it is designed to "aid cooling by providing a low-pressure area" and "streamline airflow". Because it is designed as a removeably piece I don't think it is critical. Although I suspect it helps in fuel efficiency as part of the overall redesign, I doubt it alone would make for a major impact (but could be noticeable). IMO, it also is beneficial in keeping water out of the engine compartment. I am still amazed how clean my engine compartment is even though my Jeep is a DD, and has even done stream crossings off-road.

 

I took mine off today unintentionally permanent. I had crawled under to look around as I experienced the Death Wobble and thought that I'd move that out of the way. But, it wasn't coming off too easily so one big tug later, it was on the floor. So, we'll see if there's any hit to mileage.

 

I would suspect that if it were critical Mopar would not offer a front skidplate that requires removal of the airdam to make room for the skidplate that, because of shape, could not do anything that the air dam may have been doing.

I added a winch and bumper in addition to the airdam removal and haven't noticed any notable fuel mileage loss.

 

I took it off using the drywall screw method. It came off easily, but there's still a rattle. I thought the rattle was from the heatshield/airdam/crappy plastic thing, but it isn't. It seems like there's play at the top of the shock tower and it makes a clicking sound over bumps in the road. Going to the dealer tomorrow to get it checked out.

 

Mine got torn off by a rock approx. 2 months ago. I didn't notice any change in mileage or the hood lift problem that some people complain about.