Yup... idling isn't the time when your engine is happiest.

RE: For diesels... pareho lang talaga. Any engine has to get up to operating temperature to operate efficiently, and if you cut down idling time, you cut down cold running time.

Kung sigurista ka sobra, you can even put an engine heater and a pre-lube pump in your car. This ensures that you will spend nearly no time running on cold lube or dry parts.