There is no need to be so nasty, we are simply providing our opinion on copper vs iridium plugs.
Wasn't nasty! The idea is to get better gas mileage and the Iridium plugs are supposed to improve mileage and by using them I can confirm if they do. Others that have used them say they work and improve spark and as it is I have some starting issues that may be either mixture or spark related since the vehicle was new. Also under the light loads I run the spark timing is at 38 BTDC and more so a better spark is probably going to help.
I know my NGK irridium plugs have enhanced my mileage, but only 1mpg.
Not worth the price of the plugs, nor the bumpy idle they impose. I'll move on to another brand of irridium next time around. NGK's suck so far for the money.
"You have to know the truth, and seek the truth, and the truth will set you free."
A year ago I installed a higher output coil and a few weeks later installed bosch platinum +4's. I was expecting miracles. After a year I averaged nothing noticeable, and at the same time it never quite idled right. There was always random misfiring. 2 weeks ago I installed standard autolite coppers and overgapped them to .065. The truck has never run better! My theory was the platinum is made to last longer but doesn't conduct as good as copper. So my new plugs will need to be changed more often, but why suffer with a rough idle for 100K miles between plug changes and then replace them with the same crap that doesn't idle smoothly right? I'd rather change them more frequently and maintain a perfectly smooth idle. It's been idling so smooth now that my wife keeps freaking out at traffic lights because she thinks the truck stalled- because you can't feel it running anymore. It's never done that since we got it in 1999 with 5K miles on it.
Can anyone tell me what would be the best brand and model spark plugs to buy for best MPG?
As I understand things, pretty much any plugs work fine when first installed, but some plug types (such as platinum and iridium plugs) will last much longer before they become corroded. And once a plug becomes corroded, FE will drop (until you either replace the plug, or at least pull it and again clean and gap the plug). So the main thing you are buying with a platinum or iridium plug, is that they can be installed and then left alone for much longer periods of time (than traditional plugs).
However, if you really want the best FE, I suggest you take the extra effort to have your plugs "indexed" (where you control which angle the plug gap is facing in the engine, search this forum for more info on indexing plugs). Indexing does add an extra couple of minutes labor to the time to install the plugs (and worst case, you might also have to buy a cheap washer to adjust how the plugs screw into the socket when you index a plug). However, that's a very small extra cost (to index the plugs, instead of just installing them blindly) when you change your plugs. But with with platinum or iridium plugs that doesn't occur very often (so that really is a very low extra cost), and that indexing will likely make a little improvement in both the "power" and FE of the engine (the power boost being more important to the racing crowd, the FE boost being more important to members of this forum).
BTW: Yes, I had my mechanic index my plugs when I last had my plugs changed. And yes, the indexing did seem to make a (small but) noticeable difference in both how "smooth" the engine idled, and I think my FE went up a small amount as well. So while indexing didn't make a huge difference, it really did seem to "help". And since it's so cheap to get these benefits, why not? Granted most outside of the racing crowd have never heard of indexing, but that doesn't mean that this trick doesn't also help FE (in addition to the performance boost that racers use this trick for)...