GMC 2011 Sierra Owner's Manual page 317

To save fuel, run the engine for only
short periods as needed to warm
the vehicle and then shut the engine
off and close the window most of
the way to save heat. Repeat this
until help arrives but only when you
feel really uncomfortable from the
cold. Moving about to keep warm
also helps.
If it takes some time for help to
arrive, now and then when you run
the engine, push the accelerator
pedal slightly so the engine runs
faster than the idle speed. This
keeps the battery charged to restart
the vehicle and to signal for help
with the headlamps. Do this as little
as possible to save fuel.
Slowly and cautiously spin the
wheels to free the vehicle when
stuck in sand, mud, ice, or snow.
See Rocking Your Vehicle to Get
It Out later in this section.
If the vehicle has a traction system,
it can often help to free a stuck
vehicle. Refer to the vehicle's
traction system in the Index. If stuck
too severely for the traction system
to free the vehicle, turn the traction
system off and use the rocking
method.
If the vehicle's tires spin at high
speed, they can explode, and
you or others could be injured.
The vehicle can overheat,
causing an engine compartment
fire or other damage. Spin the
wheels as little as possible and
avoid going above 55 km/h
(35 mph).
For information about using tire
chains on the vehicle, see
.