Lincoln 2016 MKZ HYBRID Owner's Manual page 178

Why does my engine stay on when it is extremely cold outside?
Why does my engine rev up so high sometimes when I accelerate?
What is the fan noise I hear from the rear of my hybrid?
How far can I go in Electric Drive if I run out of gas?
What is the engine oil change service interval?
MKZ Hybrid (CC9) Hybrid Electric Vehicle (HEV), Canada/United States of America, enUSA, First Printing
Unique Driving Characteristics
Question
In order to ensure that the climate control system can begin heating
the cabin or defrosting the windshield as soon as a driver requests
it, the engine coolant temperature has to be kept sufficiently hot.
Keeping the engine on is required to maintain the correct minimum
Your vehicle's engine and transmission are designed to deliver the
power you need at the most efficient engine speed. This may be
higher than expected during heavy accelerations, and may fluctuate
during steady state driving. These are characteristics of the Atkinson
engine cycle and the transmission technology that help maximize
your hybrid's fuel economy.
The fan noise comes from a fan located outside the high voltage
battery. This fan turns on when the battery requires cooling air. The
fan speed and associated noise level will change, according to the
amount of cooling required to maintain good performance. Maintaining
the battery temperature at optimal conditions also prolongs the useful
life of the battery and helps to achieve better fuel economy. Do not
place objects on the package tray which could block air flow through
the hybrid vehicle battery cooling vents.
Running out of gas is not recommended. However, you may be able
to go about one mile, driving at 30 mph (48 km/h), if the battery has
a normal state of charge.
See Scheduled Maintenance (page 479).
175
Answer
temperature.