Which spark plugs

[Bruce]

2002 4.0 , which spark plugs to use, i was thinking on the line of NGK Iridium's, what do you guy's use.

I have also seen a lot of problems with getting the proper plug, so what would be the proper spark plug number lets say if i used the NGK's.

 

[Big Jim M]

Why would ANYONE use other than the stock sparks? The engine has been engineered around THAT plug! It does ZACKLY what the engine needs and wants.. AND it lasts for 100K! Changing sparks can ONLY make the engine worse..No matter what spark plug you wind up with the engine running CANNOT get better..
Big JIm

 

[Jason]

Plugs alone can't help improve. The motorcraft's are fine.

 

[Bob Ayers]

Go with the OEM Motorcraft double platinums, or fine wire platinums, and they will run great! Also consider changing your plug wires when changing the spark plugs.

 

[cr_the_machinist]

Just get the plain old motorcraft plugs.... anything more than that is a waist of $$$.