I've had three Jeeps and they have all had the 2.5 4cyl. and after I buy them I always wish I would have gotten the 6... The 4 cyl's have always been reliable for me but are gutless. They work fine once you wind them up but have to bottom end power. As far as gas mileage, I get 19 on average and most people are getting 17-18 with the 6's and trust me I would be willing to sacrifice 2 mpg for the 6's power and longevity.