Ford 2002 F650 Owner's Manual page 110

Driving
Using the engine block heater (if equipped)
An engine block heater warms the engine coolant, which improves
starting, warms up the engine faster and allows the heater-defroster
system to respond quickly. Use of an engine block heater is strongly
recommended if you live in a region where temperatures reach -23° C
(-10° F) or below.
For best results, plug the heater in at least three hours before starting
the vehicle. Using the heater for longer than three hours will not harm
the engine, so the heater can be plugged in the night before starting the
vehicle.
To prevent electrical shock, do not use your heater with
ungrounded electrical systems or two-pronged (cheater)
adapters.
Operating the engine
Do not operate the engine at full throttle below peak torque engine
speed (RPM) for more than one minute at a time (peak torque RPM
varies from 1200-1500 RPM depending on engine rated speed).
Monitor the oil pressure and coolant
temperature gauges frequently.
If the gauges indicate any reading is
not in the normal operating range,
stop your vehicle as soon as
possible, shut the engine off and
check the appropriate fluid level. If
an overheating condition starts to
occur, release the throttle pressure
or shift the transmission into a
lower gear, or both, until the
temperature returns to normal operating range.
110
H
L