Indeed. The vehicle revs higher while it is driving on warmup cycle as well. Shifts to every gear noticeably later, revving higher, until it's up to temp. On my 3 mile commute, I get 16mpg in summer and 13-14mpg in winter, just because the engine is on warm-up cycle for much more of that commute. During summer it will shift into overdrive on a certain 40mph section, which it won't do on the coldest winter days, for example. Thanks to the old-tech mechanical engine fan, it probably takes longer to warm up than any other vehicle, since it actively tries to cool everything down while it's already ice cold.

My lifetime is about 20mpg in mine. I'm never lifting it. If I ever oversize tires, it'll be by an inch or less. I'm on P-metric A/Ts. I have seen a number of 25mpg tanks. I drive conservatively, bleed speed on steep canyons rather than letting it downshift twice, and do not generally cruise over about 73mph. 4.0L is a lot of engine. If you let it rev high, it's gonna suck down fuel. If you did mods that require it to rev high just to function as a basic vehicle keeping up with traffic, it's gonna suck down fuel.