Buick 1994 Skylark Owner's Manual page 170

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 littlepfaster
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.