1996 with the 4.0 I think should be Champion RC12YC, These are copper core marketed as "Year-Round". Look under the hood for the sticker that displays the exact model. Gap on the 4.0 is always 0.035"

Other models may have RC9YC, RC9LYC, RC12LYC. My 1999 4.0 takes RC12ECC. 2000 and 2001 NGK ZFR5N "V-Power" coppers.

An old salt here said that one of the double platinums should work, don't remember who though. The 4.0 (and 2.5) is not a performance engine and due to increasing fuel economy and emissions expectations it was tuned pretty tight from the factory. Go with the OEM specifications for guaranteed performance.

Try searching for threads where people report issues with E3s, Bosch, and other platinum and iridium plugs lol

 

The underhood sticker tells what works best.

 

I've been running Bosch Platinum 4's in my '96 4.0 since I bought it almost 4yrs ago. NO problems and a consistant 21/17 mpg after 30,000mi. Not saying other brands won't do the same though.

Forgot to add. Life time guarantee to.

 

It's weird, I've been in the car parts biz for over 30 years. Champion plugs work great in Jeeps, Dodges, lawnmowers, snow blowers, mini bikes with Briggs & Stratton engines. Nothing else.They're junk in anything else but work great in these. For $2 a piece it's great. I just got about 50k out of a regular set of champion coppers. I'll take it. Jeep on

 

Thanks!!! I have been searching and never thought to look there. I'll trust the engineers who built the engine over spark plug ad people any day!

 

Jeep recommends NGK ZFR5N plugs in waste spark engines (2000-2001) because they run cleaner and last longer with less fouling. All previous engines use Champion RC12YC copper core plugs for the same reason. It's not unusual for the 4.0 to run for 50K miles on one set of these plugs as long as you maintain the proper gap.