For older diesels, it is more efficient to leave them running than turning them off and restarting them. And I am talking OLD diesel trucks that have indirect i

For older diesels, it is more efficient to leave them running than turning them off and restarting them. And I am talking OLD diesel trucks that have indirect injection systems. They'll smoke a hell of a lot more than just letting them idle. Still turn them off if you don't need it running. Most modern diesels 2004+ are way more efficient in this regard in consumer vehicles and modern diesel trucks are better than they used to be.