Spark plug Bosch or NGK

I use the NGK 1675 and have and factory black coils and haven't had an issue. I have had issues with with other brands.

NKGs are the exact same plug just different label and cheaper, and are much better than the stock plugs.

Yeah can go wrong with acdelco. I run Bosch in my 93 4.3

On NGK s website it says laser iridium (the oem ones) are good for 100k miles.

So far, the OP is on to something. I’m using these plugs and that are great. Next I’m going to try the NGK ZFR6T-11G Copper Nickel. These are OEM for later 2.5 motors. I have early 2.5. I’m curious how these slightly bottler plugs will run and especially since I run premium at all times. I’ll report back. But good find OP. These work great.

The 94553 Iridiums... the tip will last longer, but the gap will widen quicker as the ground electrode does not have a platinum disc on it like the Laser Platinums, so, the Laser Platinums will last longer.

The NGK iridium I mentioned before does not have the correct reach. The website says they are the same, but they are not. I think the database is wrong. When I go back to the copper NGK that does have the correct reach, the car drives better. I had all three in my hand and the iridium is shorter from the end of the threads down (reach). NGK websites say they are the same .75 reach. They are not the same in my hands. The copper plug is. NGK 4435.

I've been pulling my CR8EIX iridium plugs out to check how they are burning a lot recently. I've been seeing some light ash deposits and high speed glazing and the iridium tips of the plugs are not as hot as I would expect them to be, i.e., they are not *white*.

I've tried NGK's gaped at .28 twice now once as preventative maint. and again some 20k down the road out of curiosity and both times i'd miss under WOT.

For the OEM Bosch plugs, I would check them every 10k-15k miles at a minimum, based on what my stock plugs looked like @ 19k miles (sh!t).