Over the past year on Jeep forums, it seems all engines (WK's) get around 13-16 mpg. Of course, this is purely independent due to the right foot theory.
For what its worth, the testing we've done with the ported 4.7 TBs I've done, all of the customers have indicated about a 1 MPG increase. Of course this requires driving appropriately, but the gains for whatever reason are there.
I average 13-15 in town and about 22-23 on the highway (at 65mph). BUT, a cold-air-induction (CAI) should help a little and a better exhaust if you don't mind a bit more noise.
Hello newbie here chiming in With my 4x2 Grand Cherokee Limited im getting right at 17 in town and upwards of 23-24 on the highway, I run both Lucas and Seafoam about every 7k miles through the system to stay on top of these marks. Some might say different, however the numbers dont lie 325 to 350 miles a tank. Reground Cams and home-made CAI.
When I had my 2wd 3.7 with a ton of mods, if I drove extremely conservative I was able to get 19 city using real world math and before the gear swap I could see 28 highway using hypermile techniques.....
Now if I drove normally it was between 14-16 city and like 20 highway lol