I'm ready to do a tune up on my 1999 Jeep Cherokee XJ. The Iridium plugs look interesting, but the stock plugs have 70K on them. I do mostly in town driving and the 4.0 is stock. Changing the cap, rotor & wire assembly at the same time. Thanks in advance for your opinions.

 

platniums are fine.

 

You can use Champion RC12ECC plugs or NGK ZFR5N plugs. Both are 'Copper' plugs. Iridium or Platinum plugs are an over kill for your standard distributor ignition system. NGK ZFR5N plugs are popular plugs and are recommended by many.

 

Like Ken said stick with NGK copper for your year. I tried the platinum plugs and my 98 ran like crap. They are a waste of money.

 

What I've read says that platinum holds a gap better/longer than copper and has less resistance thus making it easier for whatever the ignition system to jump the spark across the gap......and iridium holds a gap better/longer than platinum and is even easier (than platinum) for whatever the ignition system to jump the spark across the gap.

Platinum/iridium should never be used in a tractor motor.

 

 

i bought champion platinum plugs for $2 and change each, the $15 i spent plugs is well worth it to know they'll go another 100k