GM 5.3 owners - MPG and Iridium plug question.

[splinter]

Originally Posted By: mjk
Well, this bulletin is throwing me for a loop; just found another update for older 5.3s.

Feedback?

Yes, I’ve seen that #13D-070 ACDelco spark plug 41-110 vs. 41-962 “Application Update.”

Under ‘general information’ it states one rationale is: “These plugs fall into the family pricing matrix for double platinum and iridium plugs.
The 41-962 will be less expensive for older applications and will keep ACDelco competitive in the [aftermarket]."
Only a dollar or so from most vendors, though.

I’ve experienced mix results swapping platinum plugs for irridiums in various applications and vice-versa, although the 41-110s do just fine in my Gen-IV 5.3L.

Doug Roe, a widely respected GM engineer shared, “…when you are testing and the results disagree with your hypothesis, invent a new theory and believe it!”

Good luck with ‘em.

 

[Tzu]

I have a '00 Silverado 1500 2WD with 255k, and changed to iridium at 100k and 200k. Bought AC Delcos from Autozone and did not check the gap as they had sleeves over the tip. In the summer I get about 18-19mpg and winter blend gas gets me 15. On a long trip a few years ago I did squeak out almost 21mpg but that was exceptional.

I did have a random misfire code (P0300) pop up recently so I replaced the original wires and so far it has been fine. While doing the wires, I took out the plugs at 250k just to see how they all looked and every one looked identical in the wear/color department. I had misfires on cyl. 1 and 6 but the plugs looked normal.

100k plugs are worth it for me. Our Impala 3800 uses iridium plugs too and change every 100k. 235k on that car and it runs great. 28-30mpg HGWY in summer.