In the minds of some, idling is unnecessary and wasteful. For example, the engine is allowed to idle, fuel is consumed that did not move the load and is essentially wasted. In a typical application, only 30 min. However, in colder weather, idling keeps the engine warm and in top operating condition. Many times trouble with restarting large diesel engines is more expensive and problem causing than leaving the engine running, especially if the period is less than 30 minutes.
Temperature affects the friction of lubricants in the driveline and rolling resistance of the tires.
Oil additives decrease friction from metal to metal parts, increase horsepower, increase miles per gallon for fuel thus reducing operating expenses significantly.