Is it safe to use E3 diamond fire plugs in 05-09 4.6 or should you stay with the motorcraft oem plugs? I also heard the coil packs last till about 90,000 miles than you start having problems?

 

yes it's safe, anything is better then motorcraft oem IMO

 

I don't think Diamond Fire makes a plug for the 3V motor. We're limited to Motorcraft, Autolite, Brisk or Champion at this point. NGK is working on a plug for our motors but it isn't available yet.
I got rid of the 2 piece Motorcrap plugs and went with Champions, which are running perfectly a year later.

 

I think quality wise, the best plugs are Ford's own Motorcraft Platinum spark plugs. Don't forget, it's not the design of the plug that's at fault. It's the heads of the GT having too smaller hole for the electrode shield to sit in. Carbon can fill the gap between plug and head and cause the lower electrode cover to grip the head. If the hole was bigger, there wouldn't be a problem.

I've just replaced my original plugs with a brand new set of Motorcraft plugs, but this time, coated them as per Ford's TSB in Nickel Graphite Anti-Seize Lubricant. I believe if you follow the TSB to the letter, you will have no problems with spark plug extraction in future.

 

I went with the Champion one piece plugs at 28,900 miles. Broken one getting them out. I now sleep much better now.

 

SAME HERE BROTHER, SAME HERE.

 

I just clean and reapply antiseize on the shields once a year on my oem plugs.

 

got mine out at 17.5k miles. Non broke and put in champions. Runs better imo