Buick 1994 Century Owner's Manual page 166

bags, rags, floor
mats
--
anything you can wrap around
yourself or tuck under your clothing to keep warm.
You
can
run the engine to keep warm, but be careful.
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 your headlights. Let the heater run for awhile.
164