Your 3.8 and spark plugs
 

FYI for those thinking of changing plugs. I know this has been posted a few times here and there but I just wanted to throw in another account of why people suggest you stick with the factory spec Champion plug.

Today I Changed back to factory spec Champion plugs from NGK iridium. Tell tail sign was slowly decreasing fuel mileage over the last month and a half.

Original Champion plugs changed to NGK Iridium at 107,000 klm. NGK Iridium plugs are done already at 150,000klm (only 43,000 klm). By done I mean worn out. They look clean however, the gap is well over 0.060 upwards to 0.080". When I removed the original Champion plugs at twice the mileage they were no where near that far out.

Re: Your 3.8 and spark plugs
 

Good info. We always recommend oem plugs. NGK does make some excellent plugs, and are usually used as the oe plug in a lot of imports. (they are the factory plug in several domestic models as well.) As a general rule of thumb, Autolites in Fords, Delcos for GMs, Champions in Chryslers, and NGK,Bosch,Denso for imports. There are several grades of plugs each manufacturer makes as well. Copper core, single platinum, double platinum, iridium, etc. Make sure to replace the plugs with the same grade as origininal as well. We've found, over the years, installing the factory plug produces the best results (overall).

Re: Your 3.8 and spark plugs
 

I'm quite curious. Does anyone know WHY this is happening? I would think the PCM would regulate voltage and/or current to the plug to maintain a regular spark. What is going wrong that would cause this? Why would different plug brands react like this? That just seems weird. I get why changing from Copper to Iridium would give you a different plug life, but same grade, different brand, I would expect to be fairly close.

Re: Your 3.8 and spark plugs
 

Iridium plugs run hotter. They are not what they are exaggerated about. They are supposed to last 150,000 km. I had them in my Harley, took them out after a few rides. They load up at startup and burn more fuel.
Champion to me are generally very good plugs. Problems with breaking and few years ago but are quality plugs now.