Last set of plugs I pulled from the 06 at 100000+ miles were badly eroded one or two were just barely above the porcelain. Mfg's might say 100k but better off to replace at 80k or so. From previous experience, replaced all the coils at the same time ( bit pricey but haven't had a glitch since)
I had Champion coppers before the Autolites, and they wore too quick. I like the NGK for this Jeep. I'd never seen an electrode unappear before, and I've changed a lot of plugs.
You know, many of the jeep forum guys swear up and down that those 4.0's, ( and 4.7, and 5.2 and 5.9 lol) won't run for chit on anything but champion copper plugs. I disregarded that theory since my 4.0 zj loved the Bosch platinum, and later the ngk plugs.
Original equipment on this Jeep were NGK, or Champion. I've heard the same thing. I prefer the NGK, and at $1.95 a pop, fairly cheap.
Those guys are probably right. Copper is a better conductor than platinum or iridium, but it doesn't have nearly the long life of the other 2 materials. You kind of have to make a choice; do you want to change your plugs every 30k, 70k, or 100k miles? Most people wouldn't notice the difference anyway, especially with an un-modded street car. I've also noticed that foreign cars typically prefer NKG over anything else, but "American" cars don't often care what they're running.
Well, actually, not quite. Not when the NGKs come in the motor from the factory, and I've had better success with those than the Champion copper. I've seen TONS of threads on JF, and other forums, regarding what plugs to use and I always wonder why they don't just look in the owners manual. Follow that and all is gooder. I find it odd that the NGKs are also copper core (which is why I said not quite), but last much longer.
I would be concerned that the plugs that failed were longer? Makes sense that all gaps were closed up and one electrode was gone. Pistons making contact possibly?
NGK, or Denso plugs are all that my jeeps ever ran in them. Could have been a few causes of that plug failing, but my guess was a bad/defective plug from the factory. I have had more than on cheap plug loose it gap and close up. Just figured with the heat in the cylinder and compression, along with age stuff starts to get weak. Also that little piece from that plug is long gone, so I would not even worry about it!
I checked that before installing the Autolites. The insulators are slightly different lengths, but overall exactly the same. After I saw that plug, I checked again. I put the Autolites in last year, and we don't put on a whole lot of miles (comparatively speaking), so I'd tend to believe a bad from the factory part. I'll probably pull the plugs again soon to check, but it's been running very smooth since putting in the NGKs.
Almost as much superstition/religion associated spark plug choice as there is to two-stroke oil. And often even less supporting evidence. When I was shopping for plugs for my GMC Canyon (3.5L I5) every forum thread on the subject said I would have terrible trouble with E3 plugs. Well, guess what I put in it? Ran it almost 50K on those plugs and never had any problem, I even pulled them out a coue times (not a real convenient task either) to check up on them. It didn't run any better than the originals either tho. Many of the big plug mfgs have differing levels of quality too. The plug you buy for $1.89 is not necessarily the same plug as the one you buy for $5.99.
Even if it's the same part #? Wasn't aware of that. I always thought the price difference just due to where it was purchased.
It can be. Minor variations to the part numbers can mean different materials or features in the plug. If it's the exact same part number then it most likely is the same plug. I know I save a lot by buying certain plugs in bulk "shop packs" instead of retail packaging.
