GMC 2007 Savana Van Owner's Manual page 257

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/or the fuel operated
heater exhaust system, if equipped. And
check around again from time to time to be
sure snow does not collect there. If your
vehicle has a diesel engine and a fuel
operated heater, see "Fuel Operated Heater
(FOH)" in the diesel engine supplement.
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 (or batteries)
charged. You will need a well-charged battery
(or batteries) to restart the vehicle, and possibly for
signaling later on with your 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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