Champion Spark Plugs

Whats the difference between RJ12YC and RC12YC and RC12YC5?

Thanks.

First off the R at the front of that stands for Resistor. The 12 is the heat range the Y is for the 13/16" wrench it takes I believe off hand and the C is for copper. Now the J and the C in front of the 12 on all 3 stands for the threads and length of the the tip. The only Mopar plug of them is the RJ12YC which is a Big Block plug with a decent heat range for a street or street/strip car.

r=resistor
j=13/16 hex, 14mm thread, 3/8 reach,
c=5/8 hex, 14mm thread 3/4 reach
12=heat range
y=extended tip
c=copper electrode

pretty sure i'm right