When you take off your glow plug ignitor and the engine speed drops a few hundred RPM...that is one sign of the WRONG plug for your engine/fuel combination (or your fuel is full of water). For my 2 cycle engines I personally like the OS #8 plug. They seem to last forever and they burn a bit hotter so as to not have the RPM drop as mentioned above. The OS #8 is NOT the "perfect" plug for EVERYTHING though...different engines/fuels require different plugs in some cases. Brand to brand engine/plug/fuel results WILL vary...it is a matter of finding what works BEST for YOUR engine/fuel combo and go from there.

Sorry, but there is NO simple easy answer here since there are SO many variables to the question.

Uncle Dad