Hi!
There isn't such a thing as a ".12-.15 plug" or "Car and Airplane glowplugs"...only glowplugs

!
Why your engine quits can have many reasons. Bad plug, tank and fuel lines leaking, carb not set properly, wrong fuel, too much nitro, too little nitro, worn out engine etc.
The more nitro/higher compression you have ...the cooler plug you must use.
For ordinary sport engines like OS 40-46, TT .40-46 and Magnum and so forth running on
0-15% nitro an OS 8 or Enya 3 is a good plug to choose. Higher nitro and you might have to try a cooler plug like a Rossi 5-6 glowplug or Enya 4.
But don't forget that this is a cut and try game...engines running on 0% nitro with high compression can still demand a cool plug like the Rossi 6 to develop max power.
Regards!
Jan K
Sweden