It is true that the 4.0 I6 has only ever been offered in Jeeps. The 4.0 is based on the old AMC 2.5 I4, basically with two extra cylinders added. To be specific the 4.0 was available in the 87-91 MJ, 87-01 XJ, 91-95 YJ, 93-98 ZJ, 99-04 WJ & 97-current TJ. So currently the 4.0 is only available in a TJ and the TJ is scheduled for a complete makeover in '07 at which time the 4.0 will be dropped for good, replaced throughout the Jeep lineup by the 3.7 V6. That will make for an even 20 years of 4.0 production, pretty amazing when you consider the old school technology in that engine and it will still be available in a new '06 TJ! I love the 4.0, but it is without a doubt the most antiquated engine available in the U.S., but in our case that's a good thing