I have a 2002 Ranger 3.0L /V-6 that I bought new. The first time that I changed the plugs was @ about 90,000 miles and the plug numbers on the right and left bank cylinders were different. Unfortunately that was years ago and I did not save the old plug numbers. Now all the parts stores and even the Ford dealers tell me that both left and right banks take the same number. I know that I did not imagine this but w/o the old plugs I don't know what the numbers should be or if it even matters. Any comments would be welcome.

 

These engines use a waste spark something or another (someone smarter than me will probably chime in to tell you how that works). The original plugs are platinum on one side and it mattered which side of the engine you were on because the voltage flow direction changed from side to side. Newer "double platinum" plugs have the platinum on both sides, so it does not matter where you install them its the same part number.

Does that make sense?

 

That is right. Buy Double platinum plugs and you can use same part number for all six plugs.

 

So I guess you need to run double platinum plugs? I have regular Motorcraft SP413 plugs in it. Is that going to be harmful? If so I will get the double platinums.

 

Regular plugs will work fine, just wear out sooner.

 

Thanks for all the help. It is always great to solve a mystery that the local Ford parts dealers don't have a clue what you are even talking about. One actually told me, "oh Ford just changes part numbers every once in a while so your original plugs were probably just different numbers but actually the same plugs". Really kind of sad.... Well anyway, I hope you all have a really Merry Christmas and a Happy New Year.

 

You didn't imagine the different suffix on the factory spark plugs.
For a good read on our waste spark ignition system, look in the Tech Info thread atop this forum, for "why double platinum spark plugs.