Do you guys change your factory plugs to the new iridium design? If so which one works better and best on fuel mileage.

I have '00 5.3 also. I think I'm getting almost 2 mpg less with the new iridium plugs!

I replaced mine with Bosch Platinum +4 plugs and noticed more HP and better MPG by at least 2 mpg.

I agree with the Bosch Platinum. Have used them for sometime and will continue.

When it came time to do a tune-up on my silverado i went with what was in there, the platnium plugs. Thus began approximately one month of headache trying to figure out why it was missing so bad after about a week. To make a long story short i changed the plugs but not the wires as they looked alot newer than the plugs did and that is where all the problem started. The platnium plugs are gapped at ".060 which a GM mechanic told me they no longer use because the resistance gets too high and causes carbon arcing. This is where there is too much resistance for the spark to go through the plug, so it will arc from the top post of the plug along the outside porcelain to the hex nut part of the plug thus causing the miss that i was having. I should take pictures of one of the worse plugs and post them here. It looked like a crack in the porcelain it was gouged that deep. The GM mechanic told me that they no longer use the platnium plugs even if someone brings in an older vehicle for a tune-up and it calls for the platnium plugs. They use the iridium plugs with a ".040 gap. He also told me that the only difference with the larger gap is that it is a bit of a hotter spark wich helps with cold weather starts and mileage a bit in colder climates as wel; but not all that much.

I'm liking this post. I just passed 100k, so looking for ideas of what kind of plugs/wires and other things to buy, to start replacing.

I'm liking this post. I just passed 100k, so looking for ideas of what kind of plugs/wires and other things to buy, to start replacing.

For a one time hurt always use the AC Delco plugs the good book calls for.
As upper post said the 00-01 5.3 engine has had a AC Delco spark plug no and gap change. The factor plug was 41-932 and has been changed to 41-985 at .040 gap.
Always check the latest AC plug book.
And do not re gap the plugs if they are not gaped right pitch them back and get some that are.

I always buy the Bosch Platnium +4 plugs. I put those in my 1993 Silverado and in this one and have never had any problems with them. And I do not have to worry about gapping. :D

Go with the iridiums... it's what GM specifies now.

I've heard far too many complaints from the +4 plugs, and zero from the iridiums

I think I will keep my Bosch for now until I start having problems, which I do not expect. I have had these plugs in there for about 100K so far nothing but a positive response from me

would this explain why at 38K miles, my factory stock plugs looked like they had 200,000 miles? I changed them two years ago, and I doubt they were the "new spec" even though they were oem. now my mileage is dropping some, and I keep the engine maintained very well.

so which is better, bosch +4? or iridium?

*** And do parts counters like autozone pull up the new spec if I ask for the bosch? (ie they are pre-gapped at 0.40).

would this explain why at 38K miles, my factory stock plugs looked like they had 200,000 miles? I changed them two years ago, and I doubt they were the "new spec" even though they were oem. now my mileage is dropping some, and I keep the engine maintained very well.

so which is better, bosch +4? or iridium?

*** And do parts counters like autozone pull up the new spec if I ask for the bosch? (ie they are pre-gapped at 0.40).

Bosch and GM do not go good together.
AC Delco is the only plugs to use in a GM.

As far as the change in gap or plug no goes on your truck.
It is probalbly because the wider gap plugs was running a little hot in that year and engine.

Also check the camshaft offset setting on the dist with a engine scanner.
If it is not around or within 2-3 neg or pos of 0 degrees or way off the center of the rotor will not firedead on at the plug Wire terminal and make a hotter spark at the spark plug.
Which could burn them up faster.
Also hard driving tends to wear out plugs faster.
MT

Stick with the AC plugs. You will have less problems in the long run. I have seen to many problems caused by Bosch and other brands. And I am one of the guys that have to try to find these werd problems with new plugs.

I just changed the plugs in my truck and the factory ones were ac delco/ngk iridium. I put ac back in and would bet the ngk's would be cheaper to buy. put in what it calls for ac in gm motorcraft ford and champion or whatever chrysler is using now in their junk. ALWAYS check the gap you can adjust the gap using a gapper but DO NOT just run it wider use the hole your key ring goes in to slightly bend it open and do not bang it on anything to close it up

I just changed the plugs in my truck and the factory ones were ac delco/ngk iridium. I put ac back in and would bet the ngk's would be cheaper to buy. put in what it calls for ac in gm motorcraft ford and champion or whatever chrysler is using now in their junk. ALWAYS check the gap you can adjust the gap using a gapper but DO NOT just run it wider use the hole your key ring goes in to slightly bend it open and do not bang it on anything to close it up


Yes always check the gap and also the center the tip /or platinum dots.
I find a lot of them right out of the box not set or centered right.
But the good book says not to adjust the AC-Delco platinum plugs.
If they are not set right pitch them back and get onr that is set right.
MT

I just changed to the NGK TR55 Iridiums and it seemed to smooth out the idle and accelerate a little bit smoother. Also went with MSD Super Conductor wires...A lot of the truck guys like the NGK's.

Ive seen a few instances where Bosch platinum plugs come apart and messing up properly maintained gm service trucks, resulting in removal of the heads for repair.

Stick with the stock delcos, the center electrode can break free in the boschs and end up messing up the combustion chamber before ending up stuck in a valve :2cents:

I purchased a couple of used coils for my 5.3L off of ebay for what I paid it isn't worth shipping back. I checked in my factory manual and GM uses two different style coils for this engine. Will they work for test purposes. I can change the mount slightly.