2008 Jeep Grand Cherokee Owner's Manual - Page 281

STARTING AND OPERATING 281 If temperatures are below 32°F (0°C), operate the engine at moderate speeds for 5 minutes before full loads are applied. Engine Idling - In Cold Weather Avoid prolonged idling in ambient temperatures below 0°F (-18°C). Long periods of idling may be harmful to your engine because combustion chamber temperatures can drop so low that the fuel may not burn completely. Incomplete combustion allows carbon and varnish to form on piston rings and injector nozzles. Also, the unburned fuel can enter the crankcase, diluting the oil and causing rapid wear to the engine. Stopping The Engine Before turning off your turbo diesel engine, always allow the engine to return to normal idle speed and run for several seconds. This assures proper lubrication of the turbocharger. This is particularly necessary after any period of hard driving. Idle the engine a few minutes before routine shutdown. After full load operation, idle the engine 3 to 5 minutes before shutting it down. This idle period will allow the lubricating oil and coolant to carry excess heat away from the combustion chamber, bearings, internal components, and turbocharger. This is especially important for turbocharged, charge air cooled engines. The following chart should be used as a guide in determining the amount of engine idle time required to sufficiently cool down the turbocharger before shut down, depending upon the type of driving and the amount of cargo. 5