Myth: Diesel engines need to idle for 5 minutes or more in the morning, especially on cold days.Fact: This is one of the most commonly held myths in North America concerning diesel engines.
Most engine manufacturers recommend that newer diesel engines run for no more than 3 minutes before driving.Gelling of diesel fuel used to be a problem, but refiners have worked to resolve this issue by creating winter blends that better withstand colder temperatures.
Letting an engine idle actually does more damage to the engine than starting and stopping.
Running an engine at low speed (idling) causes twice the wear on internal parts compared to driving at regular highway speeds, which can increase maintenance costs and shorten the life of the engine. 
