I read the axle housings are beefed up D44’s with 3.73 gears and CVC joints. Transmission (auto only) and transferase with have higher gears , no Rubi 4 to1 T.C. I have heard said MPG and high speed handling is why 33” tires. My guess is the 392 will average 14/15 at best based on my JLR. I get 16/17 average MPG in my 3.6 with 37’s. I carry two 2.5 Rotopax on the tailgate because I wheel with JLU’s mostly and they have 21 gals. vs my JL’s 18. Out here in the West, slow rocky trails eat up a lot of fuel and there is a lot of wide open space between fuel stops.I’m sure it’s got differt axles, transfer case and trans.