I see no benefit to doing it warm, if by somehow you have a really stuck one, the heat cycling could maybe be used to benefit but other than that, cold is best in my opinion.

 

Ditto. If I ran into a plug that's stuck, then that's probably the only case where I'd try a warm motor.

 

Decades ago i was told to run champs over autolite. In that ride, <blown 401 cid). The champs lasted 500-750 miles before they fouled. Switched to autolite and never had a fouling issue, just a gap issue as the miles piled on .

Fast forward to the current dakota with a 4.7 engine. Again, champs were recommended and i went with them at one point. Performance was good for a short period & the i started hearing a misfire under certain conditions. Not sure how many miles from the install hut it was just months went with the ngk plugs thinking i would he done with it and all was good. Never really saw an issue with them but decided to go toa copper autolite plug with a smaller then spec gap. The idea there was as time goes on, the gap widens to the spec'd gap & performance is extended to where the gap is too wide.

Fast forward to now, 8-10k miles now??? zero issues & performance is rock solid. I expect 25-35k miles out if them before they are done & need to be swapped. I went with the 3923 plug that is one step colder than stock. Super happy with how the truck has moved along with the performance upgrades.

Stick with copper and get a low resistance wire off the coil (assuming it has wires)

 

Another fan of NGK plugs; NGK 5306 specifically. As others have said, copper only, for our application. Don’t gamble with iridiums or platinums.

One thing with NGKs . . . there are tons of counterfeits on Amazon and E-bay. Be sure to source them from a reputable supplier. I haven’t had any problems with NGKs from Rock Auto.