I have heard this by a lot of people here, but I have been told by everybody I know outside of BC, parts stores etc, where I dont ask for the part number they insist on platinum becuase "that is what their computer shows is right for the L67"


I have been running AC Delco platinum plugs in the car for a while now and notice slightly better fuel economy I think, not more than 2mpg but it is around there vs brand new NGKs (not the NGKs that were doa, a second set)

Performance is not noticably better with the copper plugs

I understand the heat buildup is bad for them but the plugs look perfect, and have been in the car for 3 years, 12,000 miles.

They do not dissipate heat as effectively in Forced Induction applications. Copper and Irridium do.

Once you start increasing boost, particularly in summer, they can become bad news quickly. They can cause KR just as other causes can.

Most Turbo, Suprcharged, or Nitrous users that know their business will tell you to stay very far away from Platinum for good reason.

Your parts counter guy is NOT the know-all expert he thinks he is, and neither is his computer.

From my experience, you should have no problem running platinum plugs or more mildly modded cars as long as you go a few heat ranges colder than stock. The copper/iridium plugs are colder plugs and therefore won't cause KR as easily, however Platinum plugs aren't THAT much worse, and manufacturers use them due to their long life and relatively decent price.

I run copper plugs in my TSTE and my dad runs copper plugs in the GTP, but in the Monte Carlo & SSEi we run platinum plugs. (SSEi has 1 range colder and Monte has 1.5 ranges colder) When the GTP was running 12.5'* we were running the same plugs that we run in the Monte now. The car had no KR issues then. We changed to Autolite 103'* and although we couldn't tell how much of an improvement they were (since the car got no KR with the other plugs) they do seem to run cooler. The main reason for the switch was that we put new plugs in the car at the beginning of the year when it comes out of storage and mid-year sometime, and the copper plugs are a bit cheaper, and the GTP doesn't get nearly as many miles put on it.

The SSEi and Monte are driven daily and rack up the miles. FWIW the SSEi has had the same spark plugs in it for the last 94k miles and it still runs great and gets great gas mileage and sees no KR. Thats the beauty of platinum plugs and thats why they recommend them.

I run copper in my car because they do run colder and I don't mind changing them every 10k. Copper is what I would recommend to you, but it should run pretty well with platinum plugs if you want to run them.

Shawn

From NGK, who manufactures the AC Delco plugs AND also manufactures Platinums, Irridiums, and Coppers:

"Do NOT run Plats in a supercharged application".




This is from a phone conversation I had personally with one of their Technical Application Guru'*.

I'm sure that is what they said, I'm not doubting you at all. However GM uses them in factory supercharged cars, and as I said, we haven't had any problems running them in L67'* before. I would recommend copper or iridium over platinums, but you can run platinums if you get the right range.

I used Bosch Plat.+4s down to about mid 13s then I had to switch, as at that point (3.0 pulley) I was starting to see knock after the 8th mile.

I also lost about 2mpg by switching to copper.

-Jeremiah