I have a little over 3.5k miles on my 04 Rubicon 5 speed and I'm only getting a little over 16 mpg. Now granted it has 4.10 gear ratio and all the other factory stuff but I thought I would end up getting a little better than that. I did my first oil change and switched to synthetic. I'm not really going to pay attention to the mileage for another couple thousand mile and by then the engine should be completely broke in...