I was reading a forum on one of these Ford websites where a couple of guys were arguing about which spark plug to use in their 4.2l. One was saying he had no trouble with using platinum but the other guy said he used copper core plug which gave him more power. He said to use Motorcraft AWGF-32c plugs, I think, and gap them at .045. I went to an O'reillys and all they had in their application list of Motorcraft plugs for a '98 4.2l were platinum ones. I went ahead and bought some Autolite copper core 762s and was wondering what gap should I use. Should I go with .045 like he said or go with what the label on the truck says (.052 -.054, I think)? Thanks

 

Spark plugs are an involved subject that is most often never considered in the debate but only hearsay and opinion seem to rule the day.
Spark plugs speced for vehicles are based on longevity for the application hence made with very hard metal alloys to meet those applications and for some advertising and sales benefits.
Very often changing them is a hassle for many owners hence the long life plugs as designed.
Most plugs are said to last a 100,000 miles or about the average time many an owner keeps a vehicle before trading up.
Platinum tips are very hard and resistant to combustion erosion as opposed to softer copper tips.
You can use copper tip with no issue but expect to change them more often.
Actually changing more often keeps the motor sharper running if your inclined in that direction.
As far as Motorcraft vs Autolite, there is no difference how each works Copper or Platinum, assuming the correct hear range and reach is used.
I have 225k + on my 02 4.6 running both makes with never an issue having changed plugs about 5 times.
Don't let anyone tell you they can feel the difference in these plugs unless they needed changing due to age and mileage then there might be a perception of a difference.
It take more then 10 HP to tell any difference by the seat of the pants.
As to gap, the Platinum's may stay in gap range longer due to less erosion over time so the wider gap can be used.
For copper the erosion takes place faster. To keep the gap within reason for the longer term, start out with a smaller gap.
The difference in gap might be a perceptible in idle smoothness with the wider gap being a bit smoother as opposed to the narrower gap if you were to do an A-B test and pay close attention..
Run whichever plug type you want with the differences in mind.
Obviously there is a difference in cost between the types.I
It's your call.
Good luck.