Rc Fuel Faq
Ricec5,
Your absolutly right, however, there are always exceptions to every general rule.
Many heli engines recommend a hot plug to keep the fire lit during idle and midrange and to help keep midrange transition as crisp and clean as possible. This is usually compensated for by richening up the needles so that detonation does not occur. I know some heli fliers that add an extra head shim to help compensate as well.
Can heli engines be run on colder plugs? sure but some of the charactistics of how the engine runs may change and retuning will definetly need to be done.
Fuelman