^ Sheesh
If you are such an efficiency enthusiast you WOULD care about the gas burned. And you would benefit from grille blocking, engine blankets, and perhaps checking to see if your thermostat is working properly. And if you have researched this at all, you would already know that idling is the WORST way to warm up an engine not just because of the wasted gas and extra emissions, but because it is the slowest way to warm it up thus the engine experiences more wear from being cold longer than when it's driven straight off.