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Spark Plug analysis pls- pulled NKGs after 10k miles off n/a

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Old 08-12-05, 02:44 PM
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Spark Plug analysis pls- pulled NKGs after 10k miles off n/a

How do my plugs look?
should I use less premix?


pulled my plugs off my
90 GXL, 84 k miles,
10 k miles on plug
nearly all hwy,
premixed 1 oz/gal to .5 oz/gal

before i pulled them, power lacked quite a bit, and idle was pretty rough, like every 2 seconds I missed once.
Attached Thumbnails Spark Plug analysis pls- pulled NKGs after 10k miles off n/a-img_0972.jpg   Spark Plug analysis pls- pulled NKGs after 10k miles off n/a-img_0973.jpg   Spark Plug analysis pls- pulled NKGs after 10k miles off n/a-img_0974.jpg   Spark Plug analysis pls- pulled NKGs after 10k miles off n/a-img_0975.jpg  
Old 08-12-05, 02:58 PM
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Nice clear pictures:

Tune is good.
Oil ash deposits are very minor.
One miss every 2 seconds - no worries.

The leading plugs are worn out.
The trailing plugs are half gone.

You might try BUR7EQP for leading. (Platinums for that longer lasting experience..)

Last edited by SureShot; 08-12-05 at 03:03 PM.
Old 08-12-05, 03:07 PM
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This is too much oil ash (and a fuzzy pic.)

Old 08-12-05, 03:11 PM
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So that leads to the obvious question...what oil have you guys been using?
Old 08-12-05, 03:34 PM
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Those plugs look fine, just worn out.

I tend to go with 5k miles or so between plug changes. I'm sure I could push it a bit longer, but that's every 2nd oil change for me, and I don't like having to troubleshoot random issues, so I preemptively replace them.

-=Russ=-
Old 08-12-05, 03:37 PM
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Hell,

Mine look like that and I push mine to 12000 miles (every 4th oil change)....but sometimes that is hard to do. It all depends on how much city driving vs highway driving I do.

The last set lasted me 15000 miles because I was driving 96 miles one way to work for a month before moving. I racked up the highway miles and the plugs lasted longer.

Now, I live in the city and am constantly in stop/go traffic. I have about 7k miles on them I think I will be changing them next oil change.
Old 08-12-05, 05:23 PM
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I used castrol gtx (20w50 summer, 10w30 winter)
with sams club (coastal??) premix (this one smoked if I used anything more than 12 oz per fill,
now I am using penziol semi-syn 2-cycle (walmart), even with 18 oz I did not get smoke, but power lacked a bit
I already put in coppers, will try platinums next time

why is the #2 leading more worn that #1 leading plug?
Old 08-12-05, 10:42 PM
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Nice pics...finally!

Those spark plugs look perfectly fine for 10k miles.
They would need to be changed for optimum performance.


-Ted
Old 08-12-05, 10:43 PM
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Originally Posted by SureShot
This is too much oil ash (and a fuzzy pic.)
It looks a *little* oily, but that could be the type of gas you're using locally.
Otherwise, they are still okay.


-Ted
Old 08-12-05, 11:13 PM
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premixing is new to me, I ran 91 or 94 octane and made sure the metering pump and lines wereclean and clear...never lost power or spoiled plugs. Is it recomended?
Old 08-13-05, 03:46 PM
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if you're not in a turbo 2 you need to lower the octane, it will cause incomplete combustion - 82 octane is ideal for a NA RX-7 due to the long combustion chamber shape. Octane is to prevent detonation, and you won't often have that in a normally aspirated (or even stock t2 s4) car.

Premixing on a stock car generally isn't recomended unless you just add a little extra in case the oil metering pump goes out. If you take out the oil metering pump, lines, and injectors you have to premix - people do this because premix burns more cleanly than regular motor oil and takes away one failure risk in the engine systems.
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