Well, I do believe what you all are saying, but I put these Bosch+4 Platinums in on 10/14/2006, and the car (2500 miles later) is still pounding strong! Really strong.

Maybe the +4s are better some way? I don't know. A friend suggested the new Bosch+4 Iridiums as my next plug, but I thought I'd try those NGKs to see the difference.

All I can say is that these plugs DO seem to make the car run better and stronger, more so than others (including rapidfires). I don't get the best milage, but I am always pounding the car and didn't change the O2 sensor after my engine problem (is is a Bosch too though). So taking other'* advice, I'm getting the AC Delco one from Rock Auto, and putting it in ASAP.

If these plugs only last for 6-12 months, I really don't mind. They have a perceptible change in power output.

-Chip
96 SSE (N/A) (K)

The NGK TR55GP'* look amazingly simular to the factory original AC Delco 41921'* at 1/3 the price. I'm thinking since NGK makes a lot of the plugs for AC Delco... I wonder if they're the same. :?: :?

That kind of sounds familiar, yeah. I can't remember where I saw that on here though.

Well I just got back from Advance Auto after looking at both the TR55'* and the TR55IX'*. They're both a very good looking plug. Only thing is though, the IX'* cost 3&1/2 TIMES more money. $1.99 for the TR55'* and $6.99 for the TR55IX'*. Does that mean they will last 3&1/2 times longer and give me 3&1/2 times more performance? :?

BTW, the Autolite XP606'* are special order.

There is NO PERFORMANCE TO BE GAINED from plugs unless you are the wrong heatrange, which you're not.

Good 'looking' plugs? Oh, buy the pretty one!

Yeah it'* a shame that after they're put in, you can't see the tips.

Macdrive, please go back and read this topic in it'* entirety, note the comments that plugs don't GAIN power, regardless of choice, and try to remember it. It'* been mentioned at least twice in this topic, and it'* a myth we need to dispel.

In addition, you cannot judge a spark plug by how good 'looking' it is. If that were true, we'd by running alot more ricer air filters here that don't flow enough air for us.

^ ^ ^
Alright then can you please so gracefully explain to me why the the Irridiums are so much better and cost so much more?

Q. What makes Iridium better?
A. Until recently, platinum was considered the best material to use on the top of an electrode because of its durability. However, Iridium is 6 times harder, 8 times stronger, and has a melting point 1200 degrees higher than platinum. Put that into a harsh environment such as an engine piston chamber, and you have a spark plug that can resist wear much better than platinum. Additionally, the DENSO Iridium Power alloy is so durable; it allowed our engineers to produce the world’* smallest center electrode (.4mm) which reduces the voltage requirements, concentrating its sparking power. Also, its smaller size, combined with the tapered U-Groove ground electrode, allows more room for the flame kernel to develop and produce a more efficient combustion.


Retrieved from: http://www.densoiridium.com/faq.php

http://www.ngksparkplugs.com/product...idiumintro.asp

http://www.ngksparkplugs.com/product...420&country=US

http://www.jcwhitney.com/webapp/wcs/...atalogId=10101

http://www.densoiridium.com/spconstruction.htm

http://search.yahoo.com/search;_ylt=...=slv1-fp&x=wrt

www.yahoo.com

www.google.com

www.howstuffworks.com

But Irridium (as already stated here) doesn't dissipate heat well enough to work in a high-boost application. This MAY hold true for High-compression applications too. So try the irridiums in your 9.4:1 compression L36, and if you're not happy, try the TR55 V-powers, or do it the other way around.