i had my plugs changed a couple months ago and then had some trouble with one or two, so i checked them all out and found that the gap was nearly .015 off the recommended gap. i know that theres a little leadway for the gaps, but how much difference could i see with opening all the plugs gaps. was it worth changing the gap or not? i dont think ive noticed much change as far as mpg, but it seems to have given me a little bit more power. but sometimes it starts pretty rough, and its not that cold. not all the time, but some mornings, it idles at normal temp really good, though. anyway, its a 2000 4wd 4.0l v6 ohv.

 

The bigger the gap the more likely you'll get a more complete conbustion. However there are side effects. It's harder on your complete ignition system, You'll see things like rougher starting ,and rougher idling.

If your motor is going to stay stock.. stick with what Ford recommended. Or a plug I like very much is the bosch platinum +2. It has an unshrouded spark which will result in better combustion. I've used them on at least 5 of my cars and give them a big thumbs up for value.

The best plug (that I use in my lightning) is the Denso IT series. It's very expensive..but worth it for my toy.

Rich