The 3.6 is a nice engine. I have a 2012 JK 2 door 6 speed with 48k and never a problem or even a warranty issue. I'm running 315/70r17 Duratracs (34s) with 4.56 gears. My JK has plenty of power in lower gears and cruises on the freeway still in the green zone. I think either engine would be...