Spark Plug Change after 56,000 miles - Pontiac G8 Forum: G8 Forums - G8Board.com
 
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post #1 of 18 (permalink) Old 11-24-2012, 06:04 PM Thread Starter
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Spark Plug Change after 56,000 miles

My gas mileage has been dropping down to high 18's to low 19's MPG when I used to get in the 20-22 range combined. Also, the car has felt sluggish and has been idling a bit on the rougher side. So I decided to try a cheap fix and change out the OE iridium spark plugs that were on the car since I bought it. The car has 56k miles on it. After pullling the plugs I could see why the car wasn't performing optimally. I thought these iridiums are supposed to last 100k. So anyways I went with NGK V-Power TR5 Copper Plugs and on startup I could definitely hear and feel the difference. Much much better idling, responsiveness, and smoother running all throughout. I'll run them for the next 15k and then check up on them.


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post #2 of 18 (permalink) Old 11-24-2012, 07:59 PM
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Nice to see an easy fix. Heard others complaining about the life of stock plugs. I only have 36k but plan on changing them anyways. Previous tune was mail order and AFR was a bit off for a while. I'm sure the plugs took some abuse as a result. With a new tune and headers installed, it may be worth changing. I have a new set of TR5's in the garage already. Glad you were able to see results.


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post #3 of 18 (permalink) Old 11-24-2012, 09:08 PM
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I changed mine and replaced with TR-5ix at 33K miles when I did my headers. They looked fine but changed them anyway.


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post #4 of 18 (permalink) Old 11-24-2012, 09:24 PM
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The plug in the picture looks like an almost new Iridium plug to me

GXP, 223/230 .634/.609 114+3, BTR .660 springs, BTR 7.425 rods, IWIS Pro Chain, Comp Rocker Trunions, VCM OTR CAI, Kooks 1 7/8 LTs, HF Cats, X pipe, Solo Axelbacks or Hooker Maxflows, Billet PCV catch can, CTS-V rear calipers. Updated GM trans mount, Camaro trans pan, HSRK w/ Omega 44005 Thermistor, BMR Rear Cradle bushings, BRM Trailing Arms, Pat G tune.

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post #5 of 18 (permalink) Old 11-24-2012, 09:39 PM
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Plug looks just like the ones I took out of mine at 115K. No signs of wear on the electrode or ground. Fresh plugs never hurt anything though.

2009 LR GT Pypes Axle backs, Pypes TriY headers, Magnaflow X pipe with cat and resonator delete, Spectre CAI, Chenry Motorsports tune, and a full set of Chenry Motorsports splitters.

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post #6 of 18 (permalink) Old 11-24-2012, 09:42 PM
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Quote:
Originally Posted by dogcat View Post
The plug in the picture looks like an almost new Iridium plug to me
Yeah, my thoughts as well.


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2014 SS "Houston Stock"

Rotofab
RCR Intake/RCR TB
LS7 MAF
SW LTs-3" catted X
Corsa Mufflers
Pat G Tune


12.08@114.45 (stock tires suck)
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post #7 of 18 (permalink) Old 11-24-2012, 10:53 PM
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I agree with the last few posts. Look like the new stock ones to me. At least at the tip. I just changed mine this week with OE Iridium at 65,000. There was no reason for me to change other than I wanted to, and got plugs cheap with promotion deal. Car was running great, and still is.

The only thing that looks a little different from the plugs I pulled is yours have a lot of build up at the base of the treads. Mine were clean, just a little discolored.

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post #8 of 18 (permalink) Old 11-25-2012, 10:50 AM
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I had a dealer service fuel injection cleaning, tech also cleaned throttle body which he felt was sticky (he's a friend) and my car feels like a new machine! It feels like the peddle is much more responsive, although I hadn't noticed it was sluggish.


I have exactly 40k, will consider new plugs next summer.
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post #9 of 18 (permalink) Old 11-25-2012, 12:39 PM
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I have been considering changing my plugs for a while now. The car runs great, always looking for a little more performance. I am putting my car away for the winter soon and I will change my plugs then.

What plugs have everyone had good luck with?

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Vararam CAI,Kooks 1 7/8" headers, Magnaflow exhaust, Cat delete,electric dumps, Pat G. tune, 4D's 20" AO6 wheels, custom L.E.D. interior/exterior light package,Polk audio subs with Kicker door speakers,3,000 watt amps. Full HID light set up, 8" SS stripe set,
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post #10 of 18 (permalink) Old 11-25-2012, 05:38 PM
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Quote:
Originally Posted by pinhead66 View Post
After pullling the plugs I could see why the car wasn't performing optimally.

??? Could you please explain what you see? None of us can see it. Looks like you wasted time and money switching to a less durable plug to me. What are we missing?

'09 GT, Vararaam, Kooks Mids + GXP Muffs, Cortex 91, Enkei PF01+Michelin Pilot SS (43lbs per corner!!)
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post #11 of 18 (permalink) Old 11-25-2012, 07:23 PM
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Lost as well... Do note there a millions of explosions that these spark plugs see, so a little discoloration is normal. If they were black and full of sutt then i would understand why.


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post #12 of 18 (permalink) Old 11-26-2012, 02:52 AM Thread Starter
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My mistake. I jumped the gun and thought there was premature wear on the electrode tips but i can now see there is none after doing more thorough research.

I did find that the gap was .035 on cyl 6 plug and .037 on cyl 8 plug. All the other plugs were fine at or very close to .040.

Could that have been the issue? In hindsight i should have just regapped those two plugs and reinstalled if that was the problem.
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post #13 of 18 (permalink) Old 11-26-2012, 08:17 AM
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Iridium plugs do look odd in comparison to the old style.

GXP, 223/230 .634/.609 114+3, BTR .660 springs, BTR 7.425 rods, IWIS Pro Chain, Comp Rocker Trunions, VCM OTR CAI, Kooks 1 7/8 LTs, HF Cats, X pipe, Solo Axelbacks or Hooker Maxflows, Billet PCV catch can, CTS-V rear calipers. Updated GM trans mount, Camaro trans pan, HSRK w/ Omega 44005 Thermistor, BMR Rear Cradle bushings, BRM Trailing Arms, Pat G tune.

20% 3M CS tint, Kicker 8's, Rockford Fosgage T1D210 in sealed box, 1,000,000 uF Cap, Kicker 1000W amp, tons of Dynamat
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post #14 of 18 (permalink) Old 11-26-2012, 01:57 PM
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Be careful with regapping Iridiums. The harder material is also more brittle. .035 might be getting a bit small on gap -- but it would have been that way since new (with use, gaps grow).

'09 GT, Vararaam, Kooks Mids + GXP Muffs, Cortex 91, Enkei PF01+Michelin Pilot SS (43lbs per corner!!)
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post #15 of 18 (permalink) Old 11-26-2012, 02:13 PM
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just swapped to tr6's instead of the tr55's....runs good



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post #16 of 18 (permalink) Old 11-26-2012, 03:05 PM
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What is everyone running iridium or platinum? Everyone I talk with has different opinions.

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post #17 of 18 (permalink) Old 11-26-2012, 03:16 PM
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What is everyone running iridium or platinum? Everyone I talk with has different opinions.
Iridium if long service life is your goal, copper if you're cool with changing them 1-2 times a year, platinum never (on these engines at least - though I never really liked platinum plugs, ever)

Going to be trading in my G8 in January or February, 2013. It's been a good run. Thanks all. See you in the for-sale section soon as I pawn off some parts...

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post #18 of 18 (permalink) Old 11-27-2012, 02:37 PM
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@travelphile, I’m very happy to read you’re able to experience your G8 with great joy again.

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Have you checked into GM Owner Center? You can maintain service history, check on warranty or recall information, and more. Visit my.gm.com!
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