All,

I don't know much about plug heat ranges, however I have a darn near new set of Denso Iridium IT20 plugs that I had in my 99 Lightning for a month and changed out when I added spray.

My 2002 FX4 is due for a plug change and the Denso site calls for IT16's. The next plug available plug is IT20's. All Lightning and Harley models call for the IT20's and standard 5.4's call for the IT16's, however when you get into the 2007 5.4 trucks, it moves back to the IT20's.

In the summer, recommendations are to run a plug with a higher heat range. What I don't know is if the IT20 is a higher heat range than the IT16. My guess is YES, but sometimes it works backwards.

Getting to the bottom, I wonder if anyone knows if I will harm my motor by running this set of Denso Iridium IT20's in the truck. I'd sure like to use them, as they are new and cost a bunch.

Thanks for any help you can provide.

 

I would think the L and Harley (do to the supercharger) Call for a lower heat rang plug.
I know when I first went with a blower I needed to go to a cooler plug.
With that being said,,I really don't think you would hurt anything buy going with one range cooler plug in you N/A motor.
So the IT16 is a hotter plug then the IT20 according to what your saying.

Phil

 

The it-20 is the cooler plug. I've heard that too cool a plug will carbon foul easier if you do much short distance driving where the engine does not run long enough at full temp??
Considering the price, I'd give them try rather than let them sit!

 

Seeing it's winter, I usually hit the auto-start and let the truck warm up. I'm going to return the new plugs I just bought and put the Denso's in. My biggest fear is causing engine damage with these plugs, but that doesn't seem to be the case. Obviously, I don't want to have to pull them out in a month either as the job is a PITA, for anyone who's dealt with them.