When in doubt, go to the 'source':
From Cummins.com - Performance Tips wrote:
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Operation Tips
It is best to operate your CELECT-equipped Cummins engine at speeds between 1450 and 1550 rpm.
Cummins M11 and N14 engines should operate with coolant temperatures between 158°F and 212°F.
Whenever an engine has been inoperative for more than 30 days, Cummins recommends disconnecting the wire to the fuel shut-off valve and cranking the engine until oil pressure registers on the gauge before starting the engine. This practice will prevent "dry starts" and allow oil to bearings and shafts prior to starting the engine. A toggle switch can be wired into the starting system for this.
Never operate your engine beyond high idle speed under any circumstances. When descending a steep grade, use a combination of transmission gears and engine or service brakes to control the vehicle and engine speed to less than governed rpm. Failure to do this can cause engine damage.
Allow the engine to idle 3 to 5 minutes before shutting it off after a full load operation. This allows the lubrication oil and coolant to carry heat away from the combustion chamber, bearings, shafts and turbocharger and helps prevent carboning the engine oil.
