spark plug wear

What octane of gas do you use in your Grand Prix? The 3800 II Supercharged is supposed to run on 91...though, I use 89 most of the time.

some platinum plugs have a very sharp thin center electrode. GW

Running the best they'll sell, 93 octane, I've put a tank full of regular in it once and that was a few years ago

These are labled AC Delco 12568387 ITR4A 15

Just wanted to check. I know some people just use standard 87 octane.

That is an Iridium spark plug with a very thin center electrode and possibly a chisel point ground electrode.

And they wonder why performance sucks and the engine doesn't stand up.

Actually, I run my car on 89, as the 91 is around $1 a liter up here (Ontario, Canada). The car runs fine on it, but I do put the 91 and even 94 in every once in a while.

I feel your pain - I'm in Ontario too. But MANY of these vehicles will actually give enough improvement in fuel consumption using the higher octane fuel to pay the difference - or very close. A supercharged 3.8 will detune significantly to run on 87 or 89.

I too have heard that quite a bit. Though, I don't really notice any difference between running my car at 89 and at 91. When I first bought it, the only gas I put in it was 91, but as the gas prices started to climb, I couldn't do it anymore. I got difficult to see 80.0 a liter on the sign, and then realize that I had to pay 92 a liter. But, that's what I get for buying a Supercharged car.

I have an '06 supercharged 3.8. My limited experience so far (3000 miles on a 13,000 mile car) shows it actually does better, mileage- wise, on 86/87 octane than on the high grade stuff. I can't 'feel' any performance difference, but I'm sure there is some.

Of course, this is a Series III, not a Series II, so YMMV.

I can tell a difference in 99 GTP. Normally I run 93 sometimes 92. The best mileage was with the 92 but its 10% ethanol. That may make the difference.

Yep, went out and bought 6 of 'em this morning. Expensive little suckers..... Gonna swap 'em out tommorrow, just won't let them go another 100K miles before I pull 'em next time, maybe 50K?

I gotta admit it's been awhile since I pulled plugs from a car, do it all the time in my trucks (the gas models anyway), but these sideways mounted V6's and my few spare moments have driven me to (alas!) let somebody else do that lately....so this was my first encounter with that particular configuration....live and learn.....appreciate the input

Ethanol fuels GENERALLY give lower mileage as ethanol has less heat value per unit.

Can't the Series III run on regular 87? If memory serves, GM doesn't require the Series III to run off higher octane.

Welcome to the world of $15 spark plugs ;-)

Glad to help.

Ethanol sucks in comparison to gasoline. Any legit scientific info on the web will agree.

GW

That's what I thought. I remember that being one of the 'big improvements' of the Series III. Having a Series II, it says in the owners manual to use no less then 91, but like I said, I do use 89 most of the time.