I just pulled the plugs out of my 98 4.0 to do a compression check and found one of the Champion RC12LYC had a loose ground electrode. The weld is weak and the electrode wobbles around easily by moving it with my fingers. That could have done a lot of damage.
They have been in there 40K miles and performed flawlessly, but now I'm worried that if I use cheap Champion plugs again I might be real sorry.

What do you guys use and why?

 

OEM champian Copper or Autolite Copper. They work the best for me. So I use what has not given me any problems.

 

NGK Iridium. Install and forget for 100,000 miles. I put 90,000 on them in my '87. Never a hiccup.

I hate Champion plugs. Cheaply made and prone to failure. I have had too many defective ones with just a few miles on them.

 

Here's a spark plug application chart you can refer to for plug selection:

 

used to run autolite then switched to NGK. i prefer the NGK but the local places don't sell them anymore for some reason. can't stand that champion junk.

 

Thanks for the replies. I've always liked NGK plugs. I think I'll pick up a half-dozen FR5-1 plugs.

 

My 97 has been running Champion RC12LYC, gapped at .035", for the last couple months just fine. They replaced fairly new looking Bosch FR9HC. Cant say if the Champions helped however as i replaced the cap/rotor, plug wires and coil along with them. And cleaned up the engine grounds which probably helped more than anything else.

 

I only run original Champion plugs in 4.0's.

 

Switch to NGK you'll be glad you did.

Even Richard Petty uses NGKs now.

 

I was chasing a rough idle for months on my '99. Checked everything. Idled fine when cold, bur when it warmed up, it would miss and idle really rough. I finally gave in and changed the autolites for champion coppers. Idle problem was gone. I would not have believed it if I had not experienced it.

 

I have NGKs in mine. Seem fine. 20,000 miles or so on them.

 

Mostly correct, but for NGK the ZFR5Ns are a better option for all 91+ XJs than the FR5-1 (not that the FR5-1 won't work, but the ZFR5N is a better match to the OE Champion RC12LYC, while the FR5-1 has a slightly shorter and shielded electrode, and of course the ZFR5N was the OE plug in later XJs). I run the ZFR5Ns in my 95 XJ and they work great, noticed a slight improvement in idle over the Champion RC12LYCs (which only had a few thousand miles on them so the difference wasn't due to wear).

 

Well, Autolite plugs are made by FRAM. So what did you expect? Quality?

 

I can't do it. Besides the fact I just changed the plugs for the hell of it and only have 72k miles on my 4.0L, I've seen silly idling problems from running different plugs other than the factory Champions. To each their own on this one, I won't argue. If I had issues with champs, I'd go NGK being as that's usually my "go-to" brand anyway.

 

The standard Champions work best in my 4.0. I've tried a few different ones in over the last 14 years and it always runs better with the Champions.