Seems that platinum and iridium plugs seem to be the norm anymore so they can have a 100k change interval.

Aside from longevity do they offer anything over the copper plugs?

They work good but don't go 100,000 on them they still age and imho should be replaced earlier, those running them that long risk the gap changing and the coils working too hard on cop applications

According the NGK there is a performance benefit. Just don't gap them.



Link to original video: https://www.youtube.com/watch?v=UGdAxlEO26I

I just pulled the original set from our 2005 Buick Lacrosse with 115,000 miles. They were still very close to the factory gap and showed little erosion.

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Aside from longevity do they offer anything over the copper plugs?

Any performance or fuel economy improvement? No. They do seem to go a long time. I changed my 100K iridium plugs at 105K and they were hardly distinguishable from the new ones. I always recommend the same brand and type as OEM for a replacement spark plug.

The best benefit is if you have an engine that is a b**** to change plugs you can do it less often. Think those are rare. Nope.

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Originally posted by Black92LX:
Seems that platinum and iridium plugs seem to be the norm anymore so they can have a 100k change interval.
Aside from longevity do they offer anything over the copper plugs?

You don't get the 100k out of them if you don't have the newer coils to power them.
My '03 Tundra doesn't qualify.

That's what the dealer told me. Are they full of it?

Dealer sounds full of it. Power required to spark a gap is related to the medium through which the spark must jump and the gap itself.

I tested the Delco plugs with a U groove ground electrode extensively and with statistics. The addition of the groove did improve my fuel economy. This was proven by the statistics of thousands of miles before and after the change. If you have a choice of plugs, you may want to choose those having a special configuration at either the ground electrode or center post.

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I always recommend the same brand and type as OEM for a replacement spark plug.

My mechanic does the same. I think this is probably good advice.

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Originally posted by arfmel:

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I always recommend the same brand and type as OEM for a replacement spark plug.

My mechanic does the same. I think this is probably good advice.

I have always had Fords so I have always used copper autolites (they make motorcraft plugs).
About to do a Chevy was going to use Autolite again or should I go with ACDelco?

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Originally posted by hrcjon:
The best benefit is if you have an engine that is a b**** to change plugs you can do it less often. Think those are rare. Nope.

This. With a V6 and front wheel drive changing ever 100,000 is worth the cost. Add in coil-packs on each cylinder and I will continue to use these plugs. Add in they are the factor plugs in my car.

My mechanic would use ac/delco.

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Originally posted by comet24:

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Originally posted by hrcjon:
The best benefit is if you have an engine that is a b**** to change plugs you can do it less often. Think those are rare. Nope.

This. With a V6 and front wheel drive changing ever 100,000 is worth the cost. Add in coil-packs on each cylinder and I will continue to use these plugs. Add in they are the factor plugs in my car.

I am getting ready to do a Chevy Silverado so this is not an issue.

Our two newest vehicles are V6 Toyotas both have well under 50k miles. I have not even looked at what is involved in doing the Highlander or Sienna and don't plan on looking until it is time. No need to dread the job for years.

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Originally posted by arfmel:
My mechanic would use ac/delco.

The ACDelcos are .40 more a plug I think I can splurge for the extra $3.20.

I have found that the plug may look fine but the insulator starts to deteriorate over time so I change my plugs around 30K miles for the best gas mileage.

I use the AC/Delco copper plugs and take my index plate to Advanced Auto Parts and pick out the plugs that the open electrode faces the intake valve. This is the same procedure that Honda uses when they divide the plug radii into four sections and determine the each cylinder thread index to select the plugs like A, B, C, or D.

My engine was rated for 17 MPG on the highway and that was the best I could get. So I raised the carb, added MSD-6 CD, adjusted the pressure regulator, and indexed the plugs. After these mods, the highway mileage went to 20 to 21 MPG.

If you've got an engine with cylinder deactivation like the late model Hemi motors from FCA, anything other than plain old 3 buck copper plugs can mess up how the MDS system operates and cause you problems.

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I am getting ready to do a Chevy Silverado so this is not an issue.

A hint for these: jack or hoist it, remove the front wheels and the plastic wheel house (a plier is needed for the dozen push pins), and everything is right there, easier than climbing over and lying on top. Also have some wires on hand, as they tend to stick and get ripped.

I changed all my wires to 10 MM. The stock wires do not last long with all the heat under the hood. You are right that the boots pull off the stock wires. I also use the ACCEL distributor cap and rotor.

It is amazing how much your gas mileage drops if the plug is facing the wrong way. That is how I found out how important it is to index your plugs. Reading about the Honda indexed plugs convinced me that indexing was the best way to go to increase gas mileage.



Assume the intake value or the fuel injector is at the 7 o'clock position of these plugs. The spark of the lower plug would be blocked so the plug needs to be rotated 180 degrees. The upper plug has been what they call "side gapping" to give better spark exposure.

I have never heard of the indexing of spark plugs before. Though it makes perfect sense.
I have always just put them in with no thought of orientation.

Happen to have a good write up on indexing so I can be sure to do it?

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Originally posted by LBAR15:
If you've got an engine with cylinder deactivation like the late model Hemi motors from FCA, anything other than plain old 3 buck copper plugs can mess up how the MDS system operates and cause you problems.

They've been using platinum plugs since 2014 or 2015. And the Silverado I used to own had a similar system with platinum plugs.