It's true that running cold is harder on an engine than running warm. The oil is thicker, and it takes a little time - very little, really - for it to flow to all the parts of the engine that need it.
But letting the car sit while the engine is running doesn't help anything. It just wastes gas and pumps out needless fumes. You might as well get on your way.
All you need to do is drive your car gently until the engine is warmed up. No smoky burn-outs first thing in the morning. Just go easy and keep those engine RPMs down until everything's toasty, and you'll be just fine.
Five to ten minutes of easy driving is about all it takes before most cars are ready to rev, says Sinclair.
Driving gently for a few minutes helps your brakes, too, says Sinclair. They also need a chance to warm up.
"Brakes go to from zero to 200 degrees or so in an instant with a hard stop," he says.
That kind of sudden temperature change promotes warping of brake rotors, he says. Better to make a few slow stops at first so the brakes can heat up gradually.