SOOOOO annoyed with people that clam to have the bug that don't understand............ YJ TJ JK are wrangler generations......... there is no 4.0 v6..... the Cherokee and the grand Cherokee are not the same vehicle. Wranglers are not the only jeeps with letter designations example MJ XJ WJ WK KK so on and so forth......... ect ect....... its not that hard people........ been talking to this guy and he is sooooooooo clueless. On top of being clueless he is being an arse.
ok rant over sorry guys
Um, there actually is
a 4.0 litre V6 - but it's a Ford engine. The V6-244 used in the Explorer, Ranger, Aerostar, and (I think) some F-150 and E-150. :P
Also, I find it interesting that, after DCX said that the "inline six engine is dated and unsafe" (the former, perhaps. The latter, really? BMW gets consistently high safety ratings, and they've been using inline six gasoline engines for the last 60 years or so...) that General Motors should be resurrecting their inline six in VORTEC trim - with a displacement of (get this!) 242 cubic inches! (242ci ~= 4.0L. Calculated displacement of our 6-242 engine is right about 241.5ci...)
Hell, I think BMW has been using I6 engines slightly longer than Jeep has - and Willys started with the F6 engine in the late 1940s or early 1950s! Displacements of the early Jeep sixes? 226ci in L-head or F-head, 161ci in F-head (and probably L-head,) and let's not forget the 230ci "Tornado" OHC inline I6 right around 1960, with the really funky cam profile (as I understand it, BOTH valves are driven off of a SINGLE cam lobe...)
The Willys 161 and 226 ci engines predate the 196ci F-head used by AMC in the American, as I recall...
EDIT - as far as "our language" goes - in purpose, it can be likened to any "trade language" used as a variation of a native tongue - "Carny" being probably the single greatest example of this. It serves to facilitate communication between people in the know, filter out people who don't know (or assess the experience level of practitioners,) and makes communication more efficient. Same thing with doctors, lawyers, electricians, carpenters, sailors, soldiers, ... Any distinct trade will have its own language involved, which evolved in response to the requirements of the profession.