Iridium - Plugs Heat Range

[virginoil]

NGK spark Plug recommendations
1999 BUICK LESABRE 3.8 V6 K FI
Spark Plug Part No. Stock No. Plug Gap
V-Power TR55 3951 .060

G-Power TR55GP 3403 .060

Laser Platinum PTR4B-15 *5146 .060

OE Laser Iridium ITR4A15 5599 .060

Iridium IX TR55IX 7164 .060


Hi to Spark Plug experts

You can see from the NGK spark plugs recommendations the Laser Iridium ITR4A15 and Laser Platinum PTR4B-15 (heat range 4) are one heat range hotter than the standard plug TR55 (heat range 5).

Is this because the Iridium and Platinum plugs:
• can take more heat
• the platinum tipped ground electrode don’t heat as well as copper
• extra heat range required to make up for the self cleaning due to the platinium
The electrodes can extra heat as it wont wear away due the platinum tip compared to the standard electrodes on the other plug

Any other explanation in respect to the iridium plugs TR55IX the iridium plug that has a standard ground electrode ie NO platinum ?

 

[beast3300]

Heat range doesn't directly cross. The Laser Iridium "ITR4A15 and Laser Platinum PTR4B-15" are the same as the 41-101 Delco plugs made by NGK and technically the correct heat range. The material has actually nothing to do with their respected heat range. As several 3800 owner I did some brain battling these same findings once upon a time.

If you want it to run well, any of those spark plugs will work nearly identically even with the difference in material (iridium, platinum) and heat range is hardly a difference in fuel economy etc. So really it's up to you in regards to how much money you want to spend on the spark plugs and how often you want to change them. I used to run Autolite copper but since they shifted production to China I will be back to NGK v-power.

Personally in my Grand Prix it has Autolite copper 605s (equavalent to TR55/IX). And my Regal has TR6's in it, roughly two heat ranges cooler than stock.

 

[mechtech2]

virgin -
You certainly did your homework!
I would use the cooler plugs. You always want as cool af a plug that will not foul. A hot plug can cause spark knock and other problems.