Well, thanks Allen. That helped!
But seriously. I deduct from the first reply that running a cold engine (driving or idling) spells rich which hurts the engine. Now, driving will raise temps faster and therefore the harmful period will be shorter than if you let it idle till it gets hot. On the other hand I presume cooling will be less efficient at stand still idling.
So the difference in harm equals the difference in minutes for getting it hot idling as compared to driving. Right ?
Gee, I am really desperately seeking an equation/argument that will let me start her up without an anxiety attack.