Since getting my WRX last year I have got in the habit of letting my cars idle for a few minutes before driving. I've been doing some research and surprisingly found mixed views on the idea.
The whole idea of letting a car idle is to bring it up to optimum operating temp to reduce wear on the engine. However, I've read that it takes considerably longer to do so when idling, causing more wear and being inefficient.
So they say it's better to idle about 30 seconds and drive lightly for the first few miles, which will bring the car to optimum operating temp much quicker, thus reducing engine wear. Also the cat. needs to run at a higher temp to be more efficient, which when ran colder causes more build up.
I just simply wanted to protect my car best as possible, and was surprised at reading a lot of this. Of course I didn't see any real data supporting these claims, and I'm no mechanic or engineer. Maybe I'm reading to much into this, but none the less it was interesting.