Engine Warm-Up; Engine Idling - Mack Granite GU Series Operator's Handbook Manual

Engine Warm-Up

CAUTION
Idling the engine unnecessarily for long periods of time wastes fuel and fouls
injection nozzles. Unburned fuel causes carbon formation and oil dilution. NEVER
race an engine during warm-up.
Engine damage can occur if the engine is not warmed up to a minimum
operating temperature of 77°C (170°F) before putting the vehicle into full
operation.
Heavy-duty diesel engines are designed to operate at optimum efficiency
when they are running loaded at (or very near) normal operating temperature,
where efficient combustion takes place. When the engine is operated
unloaded, lightly loaded (i.e., stop-and-go operations, PTO operations, or
periods of extended engine idling) or in cold weather conditions, normal
operating temperature may not be achieved or maintained. As a result, carbon
and/or varnish build-up will occur and lubricating oil will become contaminated
with combustion by-products.
Cold weather operations place added demands on a diesel engine. When
operating in cold climates (particularly in stop-and-go operations, PTO
operations or periods of extended engine idling), minimum operating
temperature must be maintained to prevent engine damage resulting from
valve varnishing and carbon build-up.
Note: Many accessories are available for cold weather operations. Refer to the
Maintenance and Lubrication Manual for additional information concerning cold
weather accessories.

Engine Idling

Idling the engine unnecessarily for long periods of time wastes fuel, fouls
injector nozzles and can lead to valve carbon and varnish deposits. Unburned
fuel causes carbon formation and oil dilution. Shut the engine down when
prolonged loading or unloading of cargo is required.
When starting a cold engine, or if the vehicle has been parked and the engine
coolant has fallen well below normal operating temperature, a fast idle speed
of approximately 1200 rpm should be maintained to help the engine warm
up more quickly.
OPERATION 173