I am one of those who is aware of a couple of cases (reported on this forum and on a Silverado forum) where somebody used NGK branded spark plugs in place of the NGK manufactured spark plug labeled as an ACDelco 41-103 and had some misfire problems. I realize that the ACDelco plug is the exact same plug as the NGK whatever it's number is except for the label embossed into it. I know it does not make any sense, but when they changed out the NGK manufactured NGK labeled plugs for the NGK manufactured ACDelco labeled plugs, their misfire problem went away. It's almost like the spark plug wells have x-ray vision to look through the ignition coil boots!
I am one who is all for using aftermarket parts that actually meet or exceed OEM parts, and I use which ever is lightest on my wallet. But, I'll only use ACDelco spark plugs in my TrailBlazer and my Silverado because of the problems I have read. Also, I refuse to knowingly use Champion or Autolite plugs in a GM product because in my experience (going back 40+ years) whenever I tried using Champion or Autolite plugs in a GM, they either did not thread well into the engine block, or if they did thread in OK, the car ran worse with them than on the old ACDelco plugs.
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