I got better gas mileage with the platinum plugs (ac delco 41-905 ) than the stock copper cores (ac delco R45TS).

Are the ngk iridium plugs any good ?

NGK Iridium IX 7401

http://shop.advanceautoparts.com/web...ium+spark+plug

I went from the ngk iridium plugs that I was running for a couple a years back to ac delco number 2 plugs. the rapid fire plugs from the stock ones. runs better. I originally went to the ngk plugs due to the hooker shorty headers.

how did the ngks do over stock ?

they didn't do as well as stock. they didn't last as long. hence why I went back to the ac delco.

I just put on ac delco r45ts, use thoughs, theres a reason thats what the factory preferred for our cars, have fun changing them what a pita

Oh yeah and they got the ceasefire to work right out of factory.

The platinums were beter than stock. they only went bad because I put a 160 thermostat

Does running a cooler temp degrade the plat plugs? I have never heard of this before. Not saying its not true. Just would like more info before I make the same mistake.

I run ngk's in everything, never had a problem. I do have msd's on my cars though too

best thing for you to do is read the gazillion threads on plugs. everybody has the ones they like. the ones they like are the best to them. while reading the threads read how many people have switched to a different plug and ended up going back. i believe it has been proven a billion times that most cars run best with factory plugs installed.

I have a 180 degree thermostat in my cfi and it runs much better and in closed loop.

The 160 degree thermstat was making the cfi unable to run in closed loop. This was confirmed by a snap on scantool. Basically it was runing rich, which would foul any plug not just platinum. I had the 41-905 platinum plugs in my cfi for 4 years (20,000 miles most city of boston driving).

I only got the stock plugs because the parts store was sold out of acdelco platinums for my cars

my car didn't like the platinums. I went with the rapid fires is the only upgrade I went to. but the stock plugs will work fine.

I have the stock plugs but i want to try somethng better.

I'm going back to platinums or try ngk irdium plugs. the ac delco coppers suck

I'd say it all depends on the application.

Expensive plugs on a non-feedback (no O2 sensor) application is crazy.

Expensive plugs on early/primitive feedback applications (feedback carb or TBI) may be crazy, although it's less crazy than using them on a non-feedback system.

Expensive plugs on port fuel-injection systems can be VERY worthwhile. I pulled the original plugs (AC Iridiums) out of Spousal Unit's 2003 Trailblazer six-popper at 90,000 miles. They were so perfect that even though I'd already purchased replacement plugs, I verified the gaps, applied anti-seize to the originals and screwed them right back in. Currently have 140K miles on it, and it runs beautifully. The replacement spark plugs are still in the box, on the shelf in the garage.

Would I go 90K on a TBI vehicle? Not without checking them at 45K, and I don't really expect they'd be re-installed.