https://info.ornl.gov/sites/publicat...s/Pub61263.pdf
Freightliner Uses Cummins engines:
Excessive idle: Should be avoided when possible. Results in
reduced fuel economy and increased engine wear. An automatic
shutdown feature is available.
Fast idle: ISB (Interact System B) engines with the common rail
fuel system may automatically increase engine speed under cold
ambient conditions to decrease time for engine warmup under idling
conditions.
Engine warmup: Do not operate at full speed/load until coolant
temperature reaches normal operating range. Do not operate above
low idle until oil pressure is indicated.
Engine cooldown: Before shutdown, an engine should be idled 3–5
minutes after extended full throttle or high power operation.
However, under normal driving conditions, such as exiting a
highway, engine operation is generally lighter in nature and,
therefore, the 3–5 minute cooldown is not necessary
Internal combustion engines must not operate at low idle speed for
extended periods of time. This operating condition may lead to poor
engine performance. The idle shutdown feature, available on most
Cummins engines, can be programmed to shut the engine down
after a period of low idle speed operation with no driver activity. A
flashing warning lamp will inform the driver of an impending
shutdown. If an engine must idle for an extended period of time, it
should be done at fast idle (1,000 rpm or greater). The Power Take
Off (PTO) feature, available on most Cummins engines, can be
programmed to adjust engine speed with the use of OEM switches
to preprogrammed setpoints.