For engines with a nitro percentage below 10% a HOT plug will do OK when the outside temp is 15/20 degrees Celsius.
For engines with a nitro percentage between 10 and 25% a MEDIUM or COLD plug will do OK when the outside temp is 15/20 degrees Celsius.
For engines with a nitro percentage above 25% (for fools only) a COLD plug will do OK when the outside temp is 15/20 degrees Celsius. http://www.twf8.ws/new/tech/tip/glowplug.html
For engines with a nitro percentage below 10% a HOT plug will do OK when the outside temp is 15/20 degrees Celsius.
For engines with a nitro percentage between 10 and 25% a MEDIUM or COLD plug wi ...