So I decided to change my spark plugs in my 2005 GMC Sierra 1500 5.3L SLE Crew Cab this weekend with the goal of replacing them with OEM plugs, but it's turning out to be quite a mysterious adventure.

When I called the dealer (I've called two) and gave them my VIN, the only plug that came up for my truck was the AC Delco 41-962, which is a platinum plug. However, when I pulled a plug from my truck (they've never been changed), I pulled a 41-110, which is an iridium plug. I asked the dealer about this and they couldn't explain it. The 41-110 plug has not been discontinued, so that's not the issue.

Can anyone explain what's going on, here? Could this have been a manufacturing error? Was there some service bulletin (that the dealer wasn't aware of) that was issued? All I want to do is put the OEM plug in my truck, but just determining what that is is turning out to be more difficult than actually changing out the plugs.

 

I suppose that they could have been short of the platinum plug that day and the others were substituted. Happens all the time in the car plants...I believe the iridium plug is supposed to be a better plug.

I went to the NAPA site and looked up plugs for your truck.....it lists the 2 you mentioned, plus about 3 pages from other manufacturers...Bosch, NGK, Champion etc.....

Personally, if you got 9 years out of the iridium plugs, I would likely stick with those.

 

Another weird thing is that when O'Reilly Auto looks up my vehicle, their system shows OEM as iridium. I agree with you, poncho62, that the iridiums will probably be just fine. There's just that part of me, though, that isn't quite comfortable with going ahead and doing it without knowing the reasoning behind the discrepancy.

 

For anyone else who might be interested, a friend of mine found this AC Delco update dated 5/21/2013 which references the OEM spark plug change from 41-110 to 41-162 for certain model year vehicles.

 

So, I didn't have time to chime in, but the parts catalog that GM gets the P/N's from, when they told you it takes platinum plugs, is always updated with the latest recommended plugs. I have found that they regularly change spark plugs on many different engines without any forewarning. I'd go with what GM said.

 

That's not a bad idea, but all indicators point to this change being for cost reasons and not for performance reasons. My truck was built with iridiums, the iridiums have been performing very well, so I'm going to stick with the OEM iridiums.