2003
monte carlo ss
3.8L


Which spark plug should be used in the 3.8L? copper, single plat, double plat, or irrdium?

 

Platinum or Iridium. Assuming you've got 100k+ miles on your engine, it'll likely be the last plug change you do. Iridium is supposed to last a little longer, but TBH I've got 100k out of platinum too.

Definitely no copper - you'll be changing plugs all the time with zero benefit.

 

I have 196,500 miles. So doesn't matter if it's single or double platinum plug?

 

Meh. Double certainly doesnt hurt, but I wouldnt personally spend a bunch of extra money for it if there's a delta. The 2nd platinum is on/in the strap (depending on the plug brand). A regular strap's area is so huge compared to the electrode that its not like its going to wear away quickly anyways.

Looking at rock auto delco plugs, it seems like all 3 options are about the same price give or take a few cents a plug anyways (single plat, double plat, iridium). Given that, I'd probably just stick the delco 41-101s in there and call it a day. I believe that was the oem plug on the later 3800s.

 

Is 15 ft pounds the torque spec for the spark plugs? Is there any special grease that I should use since it's aluminum heads?

 

GM hasn't been consistent with this through the years of the 3800 s2/s3. Ive seen the blanket 15 ft lb called out, I've also seen it called out as 11 (for reinstall of plugs pulled for inspection/ service) and 20 (for new plugs).

Regardless, 15 is fine. I'll admit I don't torque plugs, I just do it by feel (seated + a bit of extra rotation).

Aluminum? Are you sure its a 3800, not a 3400?

All 3800s had iron heads from the factory.

I don't personally use anti-sieze, but some people do. Ive just not had an issue with plugs sticking on an iron head. You've also got to be careful on torque spec as it acts like a lube / allows more rotation before hitting the same torque value.

Id personally just skip it myself if you've got a 3800 / iron heads.

 

What about spark plug grease?

 

Dielectric? Certainly not required, but I do like to use it on the boot / ceramic as added insurance.