XJRubicon said:
NGK.
Champion is for lawnmowers!
actually champions were specifically designed to run in the 4.0. I think the engineers at Jeep would konw a little more than you about this, thats why we can get 300,000 miles + out of the 4.0 with 99 cent copper plugs. As for the later models...I've never heard they switched.
I would LOVE to see a 300k mile champion. I don't believe that possible.
Maybe they did design the champion to work with the 4.0, I would STILL never run them.
I have NEVER had a set last more then 10,000 miles. The NGK's that are in my truck have been in there since 03' and STILL it runs like a dream.
I bet they need to be replaced, but they are still running strong!
XJR