Help me understand my old spark plugs.

When I first got this truck, 35,000 miles ago, I threw in some Denso iridium plugs. I decided recently to switch over to copper, and wanted to see what the old plugs could tell me about the general health of my engine since its been in my care.

I didn't use anti-seize when I put the plugs in (the new set got a little anti-seize), but all the plugs came out relatively easily.






It looks like there was a bit of shine on the driver side plugs (maybe some gas/oil?).

What do these plugs say?

 

Looks like they're in really good shape could have left them in there longer, maybe another 20k. Iridium's are good for a long long while very hard conductor.

It appears they have some deposit on the arms though and maybe running a little lean, do you run lower octane and or any fuel additives or have you fone any induction cleaning like Seafoam?

Technically speaking you're not supposed to use any anti-seize.

 

I only run 87 octane, and in those 35k miles I have run maybe two tanks with a little lucas injector cleaner. Nothing else.
As far as other causes, I did run for a few thousand miles recently with a exhaust leak in both exhaust manifolds. The exhaust leak was worse on the drivers side, which lines up with the condition of the plugs. The fix for the leaks involved new primary cats, which might have freed up some air flow.

I am well aware of the hotly debated topic of spark plug anti-seize. I lowered the torque spec (12lbs instead of 15) and I say its better safe than seized.

 

What you're doing looks fine, you could try running mid grade for a little cleaner burn an slightly more power/timing it may help.

Honestly the best thing you can do especially after installing the new plugs assuming you haven't already would be to disconnect the battery for an hour to zero out the learned trims it may run kinda funny for the first 500 miles but after that it should run a lot better and get a more complete burn that's not too lean.

Toyota factory tunes tend to run on the rich side of things, the exhaust leaks may explain the lean condition.

 

If I pulled those plugs out of my truck I’d be a happy man

 

FYI, none of those pics matter much. You have to look at the base of the porcelain. For some reason everyone thinks the threads and top of the porcelain matter.

 

Did you notice any performance improvement with the copper core plugs versus the iridium plugs you removed?

 

Whats the problem with using anti-seize on plugs ? I’ve always used it ....should I be worried ? Lol

 

It can theoretically lead to them walking back out and in excessive amounts can foul the plug or cause other issues.

NGK coats their threads in high sheen nickel so it's unnecessary anyways.

I don't use anti-seize on plug threads but I have changed plenty that had it on them.

Doesn't seem to make much difference in my experience.

Just use the torque spec on the box or as most NGK's say run it down with your fingers till the crush gasket contacts then usually .75-1.25 turns to seat it.

 

None really -unless- you use too much. I was taught to put some on a small, clean tooth-brush or similar, then wipe most of it off the brush with a clean rag until most of it was gone, and then brush the spark-plug threads with it. In other words: "just a hint". My Dad would then wipe the threads lightly with the rag. The nice nickle-plated threads on the Denso's and NGKs supposedly perform the same function. I have heard that if you over-do it, it can "cook" on the threads and cause problems; maybe from the carrier they use. It's also awful to get off your clothes and hands.

 

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