My brother runs an Industrial Mobile Medic Service, currently he is running 13 CTD 2500 long box 4x4s (some 05 and 06s) and (hes learned his lesson) also has 4 ford oh nos. Most of it not all of them are sitting idling for extended periods of time. Question is is it better to run em at higher idle speed or lower? Or should his guys switch back forth between the different idle speeds? He has to keep em running to keep power and heat going to the ambulance sections of each truck, ( these units are sitting between 8 and 12hrs on various work sites in the bush usually on oilfield drilling/service rig sites and/or construction sites)

 

tell him to set the high idle anywhere from 12-1500rpm. this will help the injectors as well as spin the altenator up a bit more to produce more power.