Re: 3.8L JK or 4.0 TJ ? Which is better?
I've owned both. TJ and current 07 Jk. 4.0 is has lots of torque for it smaller lighter TJ platform. It is easy to work on, and is a proven engine.
The 3.8 in the JK is liveable, but nothing special. Torque range feels opposite to the 4.0. It was IMO an already proven minivan engine that jeep threw into JK platform without having to spend $$$ on finding a better engine for the JK at the time. The new 3.6 Pentistar engine is much better for the jk. The 3.8 you have to run it higher rpm to get the most out of the engine to move the heavy ass JKU. I've literally have driven mine hard its entire life, it was a DD for 4 years, but I maintain it regularly. Firm believer in that. Mine does not burn oil...yet....
I've always driven right up to redline on the long hwy British Columbia mountain drives. My JK has had Superchips tune and running on 91 oct since it was released, as i like every bit of performance out that engine. My jk is at least 1000lbs over OEM weight with all the add ons.
I have seen some 3.8's burn more oil than others, but mine has been good with little to none between changes. I have about 80,000 miles on mine.
Try to find a lower mileage one obviously, maintain it and you should be fine. For most, the JK platform is the way to go. Allot of electronics on the JK's, so more difficult to work on.
There are some great deals out there on JK's that have never seen a dirt road. Go drive both and see what platform suits you. Cheers.
Just my 2cents.
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07 Jeep JKUR, built not bought!
BW 2015 Jeep SRT