Originally Posted by jcarmich
I could just send the Iridiums back, does it really make that big of a difference, of course the little things do ad up. Every one seems to give great praise to the autolite 103 coppers.
That's because we don't have a problem with changing plugs every 20k miles or so. Iridium and platinum plugs resist fouling, standard plugs do not. The plugs you bought will last for 100k miles or a little less, but definitely at least 4x longer than standard plugs. I'd use what you have. Spark plugs, although very important, don't really add a ton of performance to any engine. You might get 3 more hp by going to AR103 plugs as compared to XP, however those won't give that 3 hp RELIABLY. In another reference, you'll have 3 more hp when you put those in, but after 10 tanks of fuel (or less) you'll be down to only 1 more hp. As time goes on, deposits will build up reducing your "gain". You're really better off using what you have already gapped to the correct gap. Then you won't need to fiddle with it for a while.
I also prefer standard plugs because
those develop deposits. It can be useful in determining engine problems. I only run those in the Focus. In the wife's Windstar I run platinums because those plugs aren't easy to change.
It's a give-take thing. If you don't understand what you're getting or giving up, then just put the iridiums you already paid for in the car and go for it.