misinformation
:agree: There's a bit of bad 'advice' on the last 2-3 pages, that one being the most offensive, but there's a few things I feel noobs like me should be aware of from the start:
1. Check your gap, never, ever trust a 'pre-gapped' plug, the odds that they are properly and consistently gapped are slim. A slightly larger-than-optimal gap may hide a rough idle, sure, but you've not *actually* improved anything, and you're going to find that often enough the gap on a plug is a few microns larger than what you want. For example, the last set of NGKs I bought were gapped at .041 - .043. I brought this down to .030 - my low-temp idle is rough, yes, however:
2. The cooler plugs, when properly gapped, result in a rough idle at low temps. On a STOCK engine this is normal until your engine reaches 140-160 degrees. You should not experience any problems once warmed up. If you do, then you probably have a bad gap (wrong plug entirely, or other issue possibly unrelated to the plug.) Hotter plugs, when properly gapped, seemed to foul up more with no noticeable difference in performance.
3. For optimal performance you can pull plugs every 30k miles, they will be dirty, deposited, but not corroded. However, plugs should "last" to 100k miles or more exhibiting problems.
4. For 'mostly stock setups, with no added boost' it doesn't matter whether you use copper, iridium or platinum tipped plugs. You're simply not going to "get more performance" out of your car, at least none you can quantify using only your 5 senses.
Plugs are not like headers, you don't just swap them to gain hp, it's more about combustion efficiency.
And most importantly, it's not what you paid for a thing, it's what you know about it. A 'stock' plug, with a proper gap, is going to be more efficient for a wider heat range than non-OE/aftermarket plugs, and as it has been stated numerous times you don't *really* need to get 'extreme' with plug temps and gaps unless you have 'extreme' performance mods (like an aftermarket turbo running 20psi+ of boost.)