Both are resistive type plugs. The "R" indicates a resistor plug and the "Q" a EMS (electromagnetic suppression) resistor plug used to reduce noise in sensitive digital electronic circuits. In automotive uses Champion lists some Saab's requiring this "Q" plug. Lawn and garden small engines substituting to the RC12YC plug works just fine. In fact Sears will send you the RC12YC as a OEM part even though the engine was shipped with QC12YC plugs.
GAP .030"
no
Yes
Rc12yc
your dum
Champion Spark Plug QC12YC
A champion RC12YC spark plug is 14mm thread diameter. The torque for this size is 18-22 foot-pounds (25 to 30Neuton·meters)
yes
I have interchanged them and it seems to work. Everything is the same apart from the hex wrench. The hex on the RN12YC is 13/16" (20.6mm) and on the RC12YC it is 5/8" (16mm).
Other spark plug brands which cross-reference/interchange with the Champion QC12YC include: NGK: BCPR5ES Denso: Q16PR-U As for what applications the spark plug fits, it fits various European applications, such as BMW, Mercedes, and Saab.
.035"