275k on original spark plugs

agb104983

New member
I thought everyone might be entertained by a little anecdote on the durability of the OEM NGK plugs in the 2UZFE V8.

To start, this is not about my 4th Gen but family members 4th Gen. They said it was misfiring under acceleration and check engine light was on. I put my scanner on it and it was a misfire on cylinder 2. I asked when the last time spark plugs were done and supposedly they had not been done at all from when they first got it at 60,000 miles. It now had over 275,000. And I would assume it’s fairly unlikely that they got changed prior to 60,000 miles so most likely original plugs.

So I pulled all the plugs and coils. All the other coils looked perfect except for the cylinder 2 coil which had a crack and some scorching marks indicating failure. Got a new set of Denso iridium plugs and swapped all of them out as well as replacing the damaged coil.

I’ve included some pictures for those that are interested. All eight plugs looked identical to this. Really impressed that somehow these plugs lasted 275,000 miles. Also impressive that even though the gap had eroded to be fairly large, the vehicle had still driven fairly smoothly and quietly when I drove it 5k-10k miles prior to this.
 

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Just did the plugs on my 2007 @ 240k miles.

I'm the second owner and was shocked to see original plugs!

No CEL or even rough idle but my MPG had gone way down so I figured I would do the plugs and PCV valve.

Crazy that it was running as well as it did on factory plugs
 

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Just did the plugs on my 2007 @ 240k miles.

I'm the second owner and was shocked to see original plugs!

No CEL or even rough idle but my MPG had gone way down so I figured I would do the plugs and PCV valve.

Crazy that it was running as well as it did on factory plugs

Plug gap looks like about an 1/8" or so!
 
Which engine?

The 4.0L 6 cylinder.

I am seeing in my owner's manual.
NGK LFR6C11 (stock 7787) and Denso K20HR-U11.

I'm seeing this on the denso website.
Just a moment...



For others w/ the v8, I'm seeing Denso SK20R11 and NGK IFR6A11.

Anyway, those are the stock numbers. Are those just copper electrodes? Should I use one of the other options, such as platinum or iridium?
Actually, it looks like there's a note below those numbers that says to use only iridium-tipped spark plugs and to not adjust the gap...
 
Last edited:
The 4.0L 6 cylinder.

I am seeing in my owner's manual.
NGK LFR6C11 (stock 7787) and Denso K20HR-U11.

I'm seeing this on the denso website.
Just a moment...



For others w/ the v8, I'm seeing Denso SK20R11 and NGK IFR6A11.

Anyway, those are the stock numbers. Are those just copper electrodes? Should I use one of the other options, such as platinum or iridium?
Actually, it looks like there's a note below those numbers that says to use only iridium-tipped spark plugs and to not adjust the gap...

Yes the stock plugs for the V6 are copper, the V8 are iridium, some V6 owners do run the iridiums in their V6s but I can't say you should or shouldn't, I let V6 owners chime in on that!
 
I changed my plugs when I bought it with 220,000 miles with orig plugs. The gap was twice as wide as the spec amount. No misfires. I went with iridiums and it runs great. They will out last the truck, but having to change copper plugs every 30,000 miles isnt even an option when lifetime plugs are available.
 
I run Denso Iridium in my v6, it's been fine.

swapped out from the regular Iridium power, to the Long life versions, didn't know that the regular Iridium power plugs were 30k plugs also, ran them all the way to the 90k mark and the gap was a little bit bigger.
 

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