I had about an hour of interstate driving so I decided to try to find what my Rubicon's MPG sweet spot was by setting the cruse control (yup they have them even on the manuals) and then resetting the Avg Mpg and driving for about 5 miles. Indiana being maybe in the top 10 flattest parts of the world, I think it was a pretty good test. I-65 between Lafayette and 465
2DR Rubicon Manual 4.10 6th Gear
75 mph - 16ish mpg @ about 2,250 RPMS
70 mph - 19ish mpg I was mostly trying to find the best speed so I didn't test at this speed much to get a good reading.
65 mph - 22.3 mpg
55 mph - 23.2 mpg
I think the sweat spot would be somewhere between 45 and 50 mph. 45 is a bit of a hard test unless your willing to be that slow ass douche bag on some long highway. Anyways I was too busy testing the other speeds