Tadge,

Which is best:

Copper, Platinum, Iridium for spark plugs?

Not racing...but my slightly modified C4 - 1996 needs new plugs. We all like performance...but longevity is good too. My ride runs a little bit rich usually. I read different points of view on the internet.....but want to get a knowledgeable Corvette Man point of view.

 

Iridium hands down....

 

Will buy some Iridium plugs tomorrow. Thanks!

 

Agree with Iridium being the best!

 

They might be the best but how "best" do you need? IOW, how much till you hit the point of diminishing returns? Sure, racers might index the plug for better results but they are after every scrap of power you can get, damn the cost. So if you get a quarter of a HP, is it worth it?

Iridium might last longer but why? I get a good set of NGKs and change them every year. You can see that if they come out sooner, they are less likely to stick in the head. Also, you can see from the plug if there is either coolant or oil leaking into it. I don't think we can read the plugs and see if it is lean or rich accurately because we have EFI but oil or coolant we can tell. I change plugs, cap and rotor every spring.

 

From what I've read, copper creates the best spark when new. Platinum and iridium wear better and supposedly resist deposit fouling better than copper.

 

Dump them yearly

 

Your 1996 calls for platinums. If you have no serious modifications, I would stick with platinums or you could get iridiums, it won't make much difference because these metals are used in spark plugs for the same purposes: long life.

The change interval is 100,000 miles so as long as the plug threads have a shiny nickel plating and/or a small amount of anti-seize is used, and the plugs are torqued properly, there is no need to pull the plugs for a long, long time.

I pulled a few of the original factory spark plugs in my 1995 when I first bought it, just to check their general condition. They were great, a light tan coating and no oil or carbon buildup. 55,000 miles on the motor at the time and it still runs awesome on the same original plugs. The car has no mods.

Hope this helps you.

 

I have pulled plugs out of awesome running cars that were over 60k. Changed plugs and they ran the same per the butt dyno. Feeler gauge had then with gaps burned more open than spec. Picked up 1-2 mpg.

 

This is a photo of one of the NGK TR55s (copper) I took out this past spring after 5 years and about 35K kms (stock LT4). All 8 looked the same. I would have cleaned and gapped them and put them back in if I hadn't already purchased a set of platinums.

 

Rock Auto AC Delco double platnium $1.5 rebate each till 12/16 Original plugs ends up about $3.25 each Thats a bargin OEM plugs.#41950 Be sure to anti-seize plugs for alum. heads

 

Pretty much what I see every spring but it wouldn't be the first time I cured an acceleration miss by changing plugs. Those are what I use. I wouldn't even bother to clean them. They come out, they get trashed and new ones go in.

 

Wow... what a bunch of tightwads. You buy a high performance car and cheap out on a set of spark plugs. I just swapped out a set of plugs and wires with maybe 40,000 miles on them. Any of you ace mechanic tightwads want to buy them, probably good for another 60,000 miles. LMAO

OBTW - I got 8 new plugs off fleabay with a AC Delco rebate and ended up with a final tally of $30.

 

Maybe I should brush mine off and sell them. 1000 miles, 1 owner, slightly used. Also have bridge for sale.

 

You must be new here.

 

What's that got to do with anything?

 

This. And don't forget the high temp never seize on the threads.

 

Tightwad? I bought a $10,000 sports car. Did you consider that there are reasons why some of us did not buy an $80,000 sports car? Also I had to do certain things to save up the $10,000 to buy this toy, and not spending more than I have to is just one thing. Being smart about money doesn't make someone a tightwad. Do you replace your air filter and serpentine every year too? LMAO

OBTW - I bought 8 new NGK Iridium TR55IX spark plugs for $50. That is not cheaping out. And those Iridiums will likely last 100,000 miles. So not only are you spending more per mile for your spark plugs, but you're pulling them more often. This car is a toy and pulling plugs in an LT1 is not my idea of fun... but maybe it's just me.

 

Not the serpentine belt but if I had an air filter, I'd be changing it every year. I have Speed Density so no MAF and I use a K&N. No, it isn't fun taking it out every year to wash it, dry it, oil it and reinstall but such is life.

What happens at 100K? It magically stops working? Are you sure there is no deterioration till it is serviceable at 100K? Of the sets I pull out, there IS deterioration. I have no issues pulling out the plugs every year. OTOH, when the PO leaves the plug in there till the service interval, well, it tends to get stiff and if it breaks, well...... I agree it isn't fun servicing the car so it is better to let it ride till you have no choice. OTOH, fixing the car is even less fun. It also gives you an indication that there is oil or coolant burning when it is slight.

 

100k is the manufacturer's recommended service interval. Yes of course there is deterioration from the moment of first use, but certainly the service interval takes this wear into consideration, and deterioration is minimal with the iridiums. New motor oil deteriorates when the engine is started after an oil change, but that oil stays in the engine for 1 year/7,500 miles because that is the service interval.

Regarding broken plugs, yes maintenance is far easier and cheaper than repair so I definitely agree with that.. The factory plugs were installed with anti-seize and considering how easy it was to remove 3 of the original factory plugs (for inspection) after 18 years, I'm not worried about removing them all after 22 or 24 years. If it were easier to access all the plugs, and I had good reason for changing them early, I would at least think about it. I would probably change the plugs early if the car lived outside (moisture, weather, etc) but I am fortunate to keep it garaged all the time, and the motor doesn't leak or burn anything.

About early maintenance... I do oil changes in the ZF6 every 3 years (~15k miles), which are not required, but that service is so very easy and that transmission is very expensive, plus it shifts smoother with fresh oil. Give me your gently used plugs and I'll give you my gently used transmission oil