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Plugs for a 2000 GTP

J

JLR

New member
Howdy; I recently purchased a 2000 Grand Prix GTP. What were the recommended plugs for the 2000 GTP back in th' day? I assume it was platinum plugs, and I want to go with whatever is stock as I see no need to do any mods for this car. I bought it for my teenage son, and it's "hot" enough already :eek: . I know there 's folks that swear by the newer iridium plugs, but iridium metal isn't necessary in my estimation. Iridium is in the same periodic group as platinum, is a little denser, and is a little more corrosion resistant at high temps, but is expensive (even more than platinum) and isn't that far ahead of platinum. It seems to me iridium was used to squeeze 10-20% more miles out of the plugs, and double the price with the help of slick marketing. So I just assume use the older plugs, and If I get 100,000 miles out of them instead of 120,000 that's fine. I appreciate your help!:th_thumbsup-wink:
 


Ah, most of those maintenance items I've done already! Especially drop the transmission pan. There's some good common sense in that article too, counters some of the hype; it's a good read.
 
Apparently 3800s eat platinum.

Thus typical recommendation of copper with very short intervals or iridum and never worry about it again.

Been covered a lot lately.
 
I wonder what the physics behind that could be . . . .Could the platinums be a little hotter than they should be? there is very little difference between platinum and irridium, both are related, and both are dense, hi-temp, and corrosion resistant. Irridum is a little better that platinum, but copper is nowhere near either. Must be something to do with plug design methinks. I was going to go with Autolite AP606's but maybe I'll just do plain 606.
 
We have a waste spark system that fires each cylinder twice as often as needed.

Would wear any plug down faster than normal.

Copper is more conductive than either.

Heat is better determined by heat range of the plug which is controlled by the insulator.

If you look at the fine print on advertising claims for plat and iridium plugs, they are comparing all plugs at 50-80 k miles where the copper was worn out long ago.

Not a fair comparison however thats advertising.
 


My wife had an '88, and later '96 Chev Corsica, and they used the exact same wasted-spark ignition system. It's been around for some time! Saves the manufacturer money, and conserves a little space under the hood, but if each plug had it's own coil, it would work better. Theory says (back when I was reading about the Corsica) that when the coil fires the plugs, the plug in the exhaust cycle that receives the "wasted" spark really doesn't spark much, supposedly because the exhaust cycle environment isn't as conductive, but that isn't completely true. Wasted energy. One of the first things I noticed about this Grand Am was the familiar coil pack. I had to change one of those Corsica coils before. A pain
 
I had a brainstorm (who'd ever think of it) and had a look in the owner's manual! :th_toothless: it said AC 41-921 plugs. I ordered some, and some wires also. Now I need to order some SC oil. Autozone, Oreilly's, and a local AC Delco store don't carry it. I understand it's synth oil.
 


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