Spark Plug requirements making me nuts

[Dave in Gig Harbor]

To all,

I have a 2008 Yukon Denali XL with the 6.2 engine. Coming up on 100k miles, so I plan on going through the vehicle and replacing fluids, O2 sensors, plugs, filters, etc. Going to add ca cold air system from K & N and then do a custom tune as well. My current problem is what spark plugs to use and at what gap.

Looking at GMC dealer websites, they all call for AC Delco 19256067 spark plugs. These are AC Delco part number 41-993. The box says Iridium spark plugs, and that is what I should have.

Here are the issues I am having:

Everything on the web says the gap should be as manufactured and it should be .040 for Iridium plugs. Mine are all .060.

The AC Delco web site shoes that the 900 series plugs are platinum. Mine are 900 series and the box says Iridium

No websites other than GMC shows these as the correct spark plugs.

ANYONE that can shed some light on this would help me calm down. I have been searching for an hour to try to verify what plugs I should have (I tend to believe the GMC parts sites) and if I can use these as gapped at .060.

Thanks!!!

 

[Dave in Gig Harbor]

May have answered my own question

Pulled the factory plug, and it is an AC Delco 41-985, GM 12571164. I bought the car second hand, but I would guess these are the original plugs. Internet info seems to say these have been superseded by 41-110, so I am going to check that out.

Amazed that the GM parts guys, all of them, show the wrong spark plug which also has the wrong gap that is recommended.

Hope this helps someone. I will post a final post when I am damn sure I know what I am talking about.

 

[lt1gmc]

In both my '02 Tahoe 5.3 and my '09 Yukon Hybrid 6.0 the original plugs were 41-985, I believe the '02 was originally gapped at .060, but the '09 which I just did 2 weeks ago at 122,000 miles was gapped at .040. I installed the recommended 41-110 in both units, gapped at .040 with no issues. The '02 has had an additional 45K miles with no issues so I believe you will be good with the 41-110 at .040.
It is NOT recommended to change the factory gap from .040 to .060 because that is too much a difference and the side electrode will not have the correct radius on it. You also risk damaging the iridium parts when bending if you slip a bit with your tool.

 

[mcarlson83]

^^ this guy??? neither of his vehicles have a 6.2 so why chime in??? im running some ngk plugs in mine tr51x i have about 10,000+ miles on mine and love them, i have a 07 yukon denali now with a 152,000 on it when i put them in it was 10 grand before that, it sees in town 5 mile commutes and 35 mile one way commutes, depends on who has the truck, no issues what so ever!

 

[lt1gmc]

Because the spec'ed plugs for all three engines are the same.

^^ this guy??? neither of his vehicles have a 6.2 so why chime in??? im running some ngk plugs in mine tr51x i have about 10,000+ miles on mine and love them, i have a 07 yukon denali now with a 152,000 on it when i put them in it was 10 grand before that, it sees in town 5 mile commutes and 35 mile one way commutes, depends on who has the truck, no issues what so ever!