Buick 2008 Allure Owner's Manual page 245

CAUTION:
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Snow can trap exhaust gases under your
vehicle. This can cause deadly CO (carbon
monoxide) gas to get inside. CO could
overcome you and kill you. You cannot see
it or smell it, so you might not know it is in
your vehicle. Clear away snow from around
the base of your vehicle, especially any that
is blocking the exhaust pipe. And check
around again from time to time to be sure
snow does not collect there.
Open a window just a little on the side of
the vehicle that is away from the wind.
This will help keep CO out.
Run your engine only as long as you must. This saves
fuel. When you run the engine, make it go a little
faster than just idle. That is, push the accelerator
slightly. This uses less fuel for the heat that you get
and it keeps the battery charged. You will need a
well-charged battery to restart the vehicle, and possibly
for signaling later on with the headlamps. Let the
heater run for a while.
Then, shut the engine off and close the window
almost all the way to preserve the heat. Start the
engine again and repeat this only when you feel really
uncomfortable from the cold. But do it as little as
possible. Preserve the fuel as long as you can.
To help keep warm, you can get out of the vehicle
and do some fairly vigorous exercises every half
hour or so until help comes.
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